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SEA · 2025 transactions
Data through 2026-10-03
| Date | Player | Type | Detail |
|---|---|---|---|
| Dec 23 | Sammy Siani | Status Change | RF Sammy Siani roster status changed by Seattle Mariners. |
| Dec 23 | Sammy Siani | Signed as Free Agent | Seattle Mariners signed free agent CF Sammy Siani to a minor league contract. |
| Dec 22 | Rob Refsnyder | Signed as Free Agent | Seattle Mariners signed free agent RF Rob Refsnyder. |
| Dec 18 | Brennen Davis | Status Change | CF Brennen Davis roster status changed by Seattle Mariners. |
| Dec 18 | Brennen Davis | Signed as Free Agent | Seattle Mariners signed free agent CF Brennen Davis to a minor league contract. |
| Dec 16 | Andrew Knizner | Signed as Free Agent | Seattle Mariners signed free agent C Andrew Knizner. |
| Dec 10 | Carson Taylor | Status Change | 1B Carson Taylor roster status changed by Seattle Mariners. |
| Dec 10 | Sean Hermann | Rule 5 Draft Minors | Seattle Mariners purchased contract of RHP Sean Hermann in the Rule 5 Draft, AAA Phase. |
| Dec 10 | Cole Phillips | Rule 5 Draft Minors | Milwaukee Brewers purchased contract of RHP Cole Phillips in the Rule 5 Draft, AAA Phase. |
| Dec 10 | Carson Taylor | Rule 5 Draft Minors | Seattle Mariners purchased contract of 1B Carson Taylor in the Rule 5 Draft, AAA Phase. |
| Dec 6 | Harry Ford | Trade | Washington Nationals traded LHP Jose A. Ferrer to Seattle Mariners for C Harry Ford and RHP Isaac Lyon. |
| Dec 5 | Harry Ford | Status Change | C Harry Ford roster status changed by Seattle Mariners. |
| Nov 26 | Casey Lawrence | Status Change | RHP Casey Lawrence roster status changed by Seattle Mariners. |
| Nov 26 | Casey Lawrence | Signed as Free Agent | Seattle Mariners signed free agent RHP Casey Lawrence. |
| Nov 21 | Trent Thornton | Declared Free Agency | RHP Trent Thornton elected free agency. |
| Nov 21 | Gregory Santos | Declared Free Agency | RHP Gregory Santos elected free agency. |
| Nov 20 | Tayler Saucedo | Declared Free Agency | LHP Tayler Saucedo elected free agency. |
| Nov 19 | Jose Gabriel Torres | Signed as Free Agent | Seattle Mariners signed free agent RHP Jose Gabriel Torres to a minor league contract. |
| Nov 18 | Alex Hoppe | Status Change | RHP Alex Hoppe roster status changed by Seattle Mariners. |
| Nov 18 | Alex Hoppe | Trade | Boston Red Sox traded RHP Alex Hoppe to Seattle Mariners for C Luke Heyman. |
| Nov 18 | Tayler Saucedo | Designated for Assignment | Seattle Mariners designated LHP Tayler Saucedo for assignment. |
| Nov 17 | Randy Dobnak | Status Change | RHP Randy Dobnak roster status changed by Seattle Mariners. |
| Nov 17 | Randy Dobnak | Signed as Free Agent | Seattle Mariners signed free agent RHP Randy Dobnak to a minor league contract. |
| Nov 17 | Josh Naylor | Signed as Free Agent | Seattle Mariners signed free agent 1B Josh Naylor. |
| Nov 16 | Tyler Gough | Trade | Los Angeles Dodgers traded LHP Robinson Ortiz to Seattle Mariners for RHP Tyler Gough. |
| Nov 6 | Ryan Loutos | Claimed Off Waivers | Seattle Mariners claimed RHP Ryan Loutos off waivers from Washington Nationals. |
| Nov 5 | Jorge Polanco | Declared Free Agency | 2B Jorge Polanco elected free agency. |
| Nov 5 | Trent Thornton | Status Change | Seattle Mariners activated RHP Trent Thornton from the 60-day injured list. |
| Nov 5 | Gregory Santos | Status Change | Seattle Mariners activated RHP Gregory Santos from the 60-day injured list. |
| Nov 5 | Ryan Bliss | Status Change | Seattle Mariners activated 2B Ryan Bliss from the 60-day injured list. |
| Nov 5 | Cole Wilcox | Trade | Tampa Bay Rays traded RHP Cole Wilcox to Seattle Mariners for cash. |
| Nov 3 | Mitch Garver | Declared Free Agency | C Mitch Garver elected free agency. |
| Nov 2 | Eugenio Suárez | Declared Free Agency | 3B Eugenio Suárez elected free agency. |
| Nov 2 | Josh Naylor | Declared Free Agency | 1B Josh Naylor elected free agency. |
| Nov 2 | Luke Jackson | Declared Free Agency | RHP Luke Jackson elected free agency. |
| Nov 2 | Caleb Ferguson | Declared Free Agency | LHP Caleb Ferguson elected free agency. |
| Oct 21 | Cole Young | Status Change | Seattle Mariners activated 2B Cole Young. |
| Oct 21 | Casey Legumina | Status Change | Seattle Mariners activated RHP Casey Legumina. |
| Oct 21 | Ben Williamson | Status Change | Seattle Mariners activated 3B Ben Williamson. |
| Oct 21 | Tayler Saucedo | Status Change | Seattle Mariners activated LHP Tayler Saucedo. |
| Oct 21 | Rhylan Thomas | Status Change | Seattle Mariners activated LF Rhylan Thomas. |
| Oct 21 | Samad Taylor | Status Change | Seattle Mariners activated 2B Samad Taylor. |
| Oct 21 | Luke Raley | Status Change | Seattle Mariners activated RF Luke Raley. |
| Oct 21 | Jackson Kowar | Status Change | Seattle Mariners activated RHP Jackson Kowar. |
| Oct 21 | Troy Taylor | Status Change | Seattle Mariners activated RHP Troy Taylor. |
| Oct 21 | Logan Evans | Status Change | Seattle Mariners activated RHP Logan Evans. |
| Oct 21 | Jhonathan Díaz | Status Change | Seattle Mariners activated LHP Jhonathan Díaz. |
| Oct 21 | Domingo Gonzalez | Status Change | Seattle Mariners activated RHP Domingo Gonzalez. |
| Oct 21 | Blas Castaño | Status Change | Seattle Mariners activated RHP Blas Castaño. |
| Oct 12 | Luke Raley | Status Change | RF Luke Raley roster status changed by Seattle Mariners. |
| Oct 12 | Ben Williamson | Status Change | 3B Ben Williamson roster status changed by Seattle Mariners. |
| Oct 12 | Miles Mastrobuoni | Status Change | Seattle Mariners activated 3B Miles Mastrobuoni. |
| Oct 12 | Bryan Woo | Status Change | Seattle Mariners activated RHP Bryan Woo. |
| Oct 4 | Miles Mastrobuoni | Status Change | 3B Miles Mastrobuoni roster status changed by Seattle Mariners. |
| Oct 4 | Cole Young | Status Change | 2B Cole Young roster status changed by Seattle Mariners. |
| Oct 4 | Samad Taylor | Status Change | 2B Samad Taylor roster status changed by Seattle Mariners. |
| Oct 4 | Rhylan Thomas | Status Change | LF Rhylan Thomas roster status changed by Seattle Mariners. |
| Oct 4 | Bryan Woo | Status Change | RHP Bryan Woo roster status changed by Seattle Mariners. |
| Oct 4 | Troy Taylor | Status Change | RHP Troy Taylor roster status changed by Seattle Mariners. |
| Oct 4 | Tayler Saucedo | Status Change | LHP Tayler Saucedo roster status changed by Seattle Mariners. |
| Oct 4 | Casey Legumina | Status Change | RHP Casey Legumina roster status changed by Seattle Mariners. |
| Oct 4 | Jackson Kowar | Status Change | RHP Jackson Kowar roster status changed by Seattle Mariners. |
| Oct 4 | Domingo Gonzalez | Status Change | RHP Domingo Gonzalez roster status changed by Seattle Mariners. |
| Oct 4 | Logan Evans | Status Change | RHP Logan Evans roster status changed by Seattle Mariners. |
| Oct 4 | Jhonathan Díaz | Status Change | LHP Jhonathan Díaz roster status changed by Seattle Mariners. |
| Oct 4 | Blas Castaño | Status Change | RHP Blas Castaño roster status changed by Seattle Mariners. |
| Sep 29 | Rhylan Thomas | Recalled | Seattle Mariners recalled LF Rhylan Thomas from Tacoma Rainiers. |
| Sep 29 | Ben Williamson | Recalled | Seattle Mariners recalled 3B Ben Williamson from Tacoma Rainiers. |
| Sep 29 | Troy Taylor | Recalled | Seattle Mariners recalled RHP Troy Taylor from Tacoma Rainiers. |
| Sep 29 | Samad Taylor | Recalled | Seattle Mariners recalled 2B Samad Taylor from Tacoma Rainiers. |
| Sep 29 | Tayler Saucedo | Recalled | Seattle Mariners recalled LHP Tayler Saucedo from Tacoma Rainiers. |
| Sep 29 | Casey Legumina | Recalled | Seattle Mariners recalled RHP Casey Legumina from ACL Mariners. |
| Sep 29 | Domingo Gonzalez | Recalled | Seattle Mariners recalled RHP Domingo Gonzalez from Tacoma Rainiers. |
| Sep 29 | Logan Evans | Recalled | Seattle Mariners recalled RHP Logan Evans from ACL Mariners. |
| Sep 29 | Jhonathan Díaz | Recalled | Seattle Mariners recalled LHP Jhonathan Díaz from Tacoma Rainiers. |
| Sep 29 | Blas Castaño | Recalled | Seattle Mariners recalled RHP Blas Castaño from Tacoma Rainiers. |
| Sep 29 | Jackson Kowar | Status Change | Seattle Mariners activated RHP Jackson Kowar. |
| Sep 28 | Logan Evans | Optioned | Seattle Mariners optioned RHP Logan Evans to ACL Mariners. |
| Sep 28 | Miles Mastrobuoni | Recalled | Seattle Mariners recalled 3B Miles Mastrobuoni from Tacoma Rainiers. |
| Sep 27 | Logan Evans | Status Change | Seattle Mariners activated RHP Logan Evans from the 15-day injured list. |
| Sep 27 | Casey Legumina | Optioned | Seattle Mariners optioned RHP Casey Legumina to ACL Mariners. |
| Sep 16 | Logan Evans | Assigned | Seattle Mariners sent RHP Logan Evans on a rehab assignment to Tacoma Rainiers. |
| Sep 15 | José Castillo | Claimed Off Waivers | Baltimore Orioles claimed LHP José Castillo off waivers from Seattle Mariners. |
| Sep 12 | José Castillo | Designated for Assignment | Seattle Mariners designated LHP José Castillo for assignment. |
| Sep 12 | Casey Legumina | Recalled | Seattle Mariners recalled RHP Casey Legumina from Tacoma Rainiers. |
| Sep 6 | Gregory Santos | Assigned | Seattle Mariners sent RHP Gregory Santos on a rehab assignment to Tacoma Rainiers. |
| Sep 6 | Gregory Santos | Assigned | Seattle Mariners sent RHP Gregory Santos on a rehab assignment to Tacoma Rainiers. |
| Sep 6 | Victor Robles | Status Change | Seattle Mariners activated RF Victor Robles. |
| Sep 5 | Joe Jacques | Outrighted | Seattle Mariners sent LHP Joe Jacques outright to Tacoma Rainiers. |
| Sep 4 | Tayler Saucedo | Optioned | Seattle Mariners optioned LHP Tayler Saucedo to Tacoma Rainiers. |
| Sep 4 | José Castillo | Status Change | Seattle Mariners activated LHP José Castillo. |
| Sep 3 | Joe Jacques | Designated for Assignment | Seattle Mariners designated LHP Joe Jacques for assignment. |
| Sep 3 | José Castillo | Claimed Off Waivers | Seattle Mariners claimed LHP José Castillo off waivers from New York Mets. |
| Sep 3 | Sauryn Lao | Claimed Off Waivers | Washington Nationals claimed RHP Sauryn Lao off waivers from Seattle Mariners. |
| Sep 2 | Guillo Zuñiga | Signed as Free Agent | Seattle Mariners signed free agent RHP Guillo Zuñiga to a minor league contract. |
| Sep 2 | Nick Anderson | Signed as Free Agent | Seattle Mariners signed free agent RHP Nick Anderson to a minor league contract. |
| Sep 1 | Donovan Solano | Released | Seattle Mariners released 1B Donovan Solano. |
| Sep 1 | Sauryn Lao | Designated for Assignment | Seattle Mariners designated RHP Sauryn Lao for assignment. |
| Sep 1 | Leo Rivas | Recalled | Seattle Mariners recalled 2B Leo Rivas from Tacoma Rainiers. |
| Sep 1 | Luke Jackson | Selected | Seattle Mariners selected the contract of RHP Luke Jackson from Tacoma Rainiers. |
| Sep 1 | Harry Ford | Selected | Seattle Mariners selected the contract of C Harry Ford from Tacoma Rainiers. |
| Aug 29 | Victor Robles | Suspension | RF Victor Robles suspended. |
| Aug 28 | Ryan Bliss | Assigned | Seattle Mariners sent 2B Ryan Bliss on a rehab assignment to Tacoma Rainiers. |
| Aug 27 | Sauryn Lao | Optioned | Seattle Mariners optioned RHP Sauryn Lao to Tacoma Rainiers. |
| Aug 27 | Emerson Hancock | Recalled | Seattle Mariners recalled RHP Emerson Hancock from Tacoma Rainiers. |
| Aug 25 | Dylan Moore | Released | Seattle Mariners released 2B Dylan Moore. |
| Aug 23 | Victor Robles | Status Change | Seattle Mariners activated RF Victor Robles from the 60-day injured list. |
| Aug 23 | Dylan Moore | Designated for Assignment | Seattle Mariners designated 2B Dylan Moore for assignment. |
| Aug 21 | Luke Jackson | Signed as Free Agent | Seattle Mariners signed free agent RHP Luke Jackson to a minor league contract. |
| Aug 19 | Jackson Kowar | Status Change | Seattle Mariners placed RHP Jackson Kowar on the 15-day injured list. Right shoulder impingement. |
| Aug 19 | Michael Fulmer | Signed as Free Agent | Seattle Mariners signed free agent RHP Michael Fulmer to a minor league contract. |
| Aug 19 | Sauryn Lao | Status Change | Seattle Mariners activated RHP Sauryn Lao. |
| Aug 19 | Casey Legumina | Optioned | Seattle Mariners optioned RHP Casey Legumina to Tacoma Rainiers. |
| Aug 19 | Jackson Kowar | Optioned | Seattle Mariners optioned RHP Jackson Kowar to Tacoma Rainiers. |
| Aug 19 | Trent Thornton | Status Change | Seattle Mariners transferred RHP Trent Thornton from the 15-day injured list to the 60-day injured list. Left achilles tear. |
| Aug 19 | Sauryn Lao | Selected | Seattle Mariners selected the contract of RHP Sauryn Lao from Tacoma Rainiers. |
| Aug 19 | Bryce Miller | Status Change | Seattle Mariners activated RHP Bryce Miller from the 15-day injured list. |
| Aug 18 | Miles Mastrobuoni | Optioned | Seattle Mariners optioned 3B Miles Mastrobuoni to Tacoma Rainiers. |
| Aug 17 | Miles Mastrobuoni | Recalled | Seattle Mariners recalled 3B Miles Mastrobuoni from Tacoma Rainiers. |
| Aug 15 | Luke Raley | Status Change | Seattle Mariners activated RF Luke Raley from the 10-day injured list. |
| Aug 15 | Logan Evans | Status Change | Seattle Mariners placed RHP Logan Evans on the 15-day injured list. Right elbow inflammation. |
| Aug 15 | Tayler Saucedo | Recalled | Seattle Mariners recalled LHP Tayler Saucedo from Tacoma Rainiers. |
| Aug 15 | Miles Mastrobuoni | Optioned | Seattle Mariners optioned 3B Miles Mastrobuoni to Tacoma Rainiers. |
| Aug 12 | Victor Robles | Assigned | Seattle Mariners sent RF Victor Robles on a rehab assignment to Tacoma Rainiers. |
| Aug 12 | Victor Robles | Assigned | Seattle Mariners sent RF Victor Robles on a rehab assignment to Tacoma Rainiers. |
| Aug 12 | Domingo Gonzalez | Optioned | Seattle Mariners optioned RHP Domingo Gonzalez to Tacoma Rainiers. |
| Aug 12 | Domingo Gonzalez | Claimed Off Waivers | Seattle Mariners claimed RHP Domingo Gonzalez off waivers from Atlanta Braves. |
| Aug 8 | Luke Raley | Assigned | Seattle Mariners sent RF Luke Raley on a rehab assignment to Tacoma Rainiers. |
| Aug 3 | Collin Snider | Outrighted | Seattle Mariners sent RHP Collin Snider outright to Tacoma Rainiers. |
| Aug 1 | Bryce Miller | Assigned | Seattle Mariners sent RHP Bryce Miller on a rehab assignment to Tacoma Rainiers. |
| Aug 1 | Bryce Miller | Assigned | Seattle Mariners sent RHP Bryce Miller on a rehab assignment to Tacoma Rainiers. |
| Aug 1 | Bryce Miller | Assigned | Seattle Mariners sent RHP Bryce Miller on a rehab assignment to Tacoma Rainiers. |
| Aug 1 | Trent Thornton | Status Change | Seattle Mariners placed RHP Trent Thornton on the 15-day injured list. Left achilles tear. |
| Aug 1 | Jackson Kowar | Recalled | Seattle Mariners recalled RHP Jackson Kowar from Tacoma Rainiers. |
| Jul 31 | Miles Mastrobuoni | Recalled | Seattle Mariners recalled 3B Miles Mastrobuoni from Tacoma Rainiers. |
| Jul 31 | Ben Williamson | Optioned | Seattle Mariners optioned 3B Ben Williamson to Tacoma Rainiers. |
| Jul 31 | Juan Burgos | Trade | Arizona Diamondbacks traded 3B Eugenio Suárez to Seattle Mariners for 1B Tyler Locklear, RHP Hunter Cranton and RHP Juan Burgos. |
| Jul 30 | Jackson Kowar | Optioned | Seattle Mariners optioned RHP Jackson Kowar to Tacoma Rainiers. |
| Jul 30 | Caleb Ferguson | Status Change | Seattle Mariners activated LHP Caleb Ferguson. |
| Jul 30 | Jeter Martinez | Trade | Pittsburgh Pirates traded LHP Caleb Ferguson to Seattle Mariners for RHP Jeter Martinez. |
| Jul 30 | Collin Snider | Designated for Assignment | Seattle Mariners designated RHP Collin Snider for assignment. |
| Jul 30 | Tyler Locklear | Recalled | Seattle Mariners recalled 1B Tyler Locklear from Tacoma Rainiers. |
| Jul 30 | Luke Raley | Status Change | Seattle Mariners placed RF Luke Raley on the 10-day injured list retroactive to July 27, 2025. Back spasm. |
| Jul 25 | Josh Naylor | Status Change | Seattle Mariners activated 1B Josh Naylor. |
| Jul 25 | Miles Mastrobuoni | Optioned | Seattle Mariners optioned 3B Miles Mastrobuoni to Tacoma Rainiers. |
| Jul 24 | Josh Naylor | Trade | Arizona Diamondbacks traded 1B Josh Naylor to Seattle Mariners for LHP Brandyn Garcia and RHP Ashton Izzi. |
| Jul 24 | Brandyn Garcia | Optioned | Seattle Mariners optioned LHP Brandyn Garcia to Tacoma Rainiers. |
| Jul 24 | Jackson Kowar | Recalled | Seattle Mariners recalled RHP Jackson Kowar from Tacoma Rainiers. |
| Jul 22 | Kade Anderson | Signed | Seattle Mariners signed LHP Kade Anderson. |
| Jul 22 | Julio E. Rodriguez | Trade | Seattle Mariners traded C Julio E. Rodriguez to Kansas City Royals for cash. |
| Jul 21 | Juan Burgos | Optioned | Seattle Mariners optioned RHP Juan Burgos to Tacoma Rainiers. |
| Jul 21 | Brandyn Garcia | Selected | Seattle Mariners selected the contract of LHP Brandyn Garcia from Tacoma Rainiers. |
| Jul 20 | Jo Oyama | Signed as Free Agent | Seattle Mariners signed free agent 2B Jo Oyama to a minor league contract. |
| Jul 19 | Brady O'Brien | Signed as Free Agent | Seattle Mariners signed free agent 2B Brady O'Brien to a minor league contract. |
| Jul 19 | Reese Lumpkin | Signed as Free Agent | Seattle Mariners signed free agent RHP Reese Lumpkin to a minor league contract. |
| Jul 19 | Reid Easterly | Signed as Free Agent | Seattle Mariners signed free agent LHP Reid Easterly to a minor league contract. |
| Jul 19 | Konni Durschlag | Signed as Free Agent | Seattle Mariners signed free agent OF Konni Durschlag to a minor league contract. |
| Jul 19 | Estevan Moreno | Signed | Seattle Mariners signed SS Estevan Moreno. |
| Jul 19 | Anthony Karoly | Signed | Seattle Mariners signed RHP Anthony Karoly. |
| Jul 19 | Casey Hintz | Signed | Seattle Mariners signed RHP Casey Hintz. |
| Jul 19 | Brayden Corn | Signed | Seattle Mariners signed OF Brayden Corn. |
| Jul 19 | Luke Heyman | Signed | Seattle Mariners signed C Luke Heyman. |
| Jul 19 | Aiden Taurek | Signed | Seattle Mariners signed OF Aiden Taurek. |
| Jul 19 | Grant Jay | Signed | Seattle Mariners signed C Grant Jay. |
| Jul 19 | Dusty Revis | Signed | Seattle Mariners signed RHP Dusty Revis. |
| Jul 19 | Isaac Lyon | Signed | Seattle Mariners signed RHP Isaac Lyon. |
| Jul 19 | Jackson Steensma | Signed | Seattle Mariners signed RHP Jackson Steensma. |
| Jul 19 | Danny Macchiarola | Signed | Seattle Mariners signed RHP Danny Macchiarola. |
| Jul 19 | Colton Shaw | Signed | Seattle Mariners signed RHP Colton Shaw. |
| Jul 19 | Lucas Kelly | Signed | Seattle Mariners signed RHP Lucas Kelly. |
| Jul 19 | Korbyn Dickerson | Signed | Seattle Mariners signed OF Korbyn Dickerson. |
| Jul 19 | Mason Peters | Signed | Seattle Mariners signed LHP Mason Peters. |
| Jul 19 | Griffin Hugus | Signed | Seattle Mariners signed RHP Griffin Hugus. |
| Jul 19 | Luke Stevenson | Signed | Seattle Mariners signed C Luke Stevenson. |
| Jul 19 | Nick Becker | Signed | Seattle Mariners signed SS Nick Becker. |
| Jul 14 | Carlos Vargas | Status Change | Seattle Mariners activated RHP Carlos Vargas from the paternity list. |
| Jul 14 | Tayler Saucedo | Optioned | Seattle Mariners optioned LHP Tayler Saucedo to Tacoma Rainiers. |
| Jul 11 | Carlos Vargas | Status Change | Seattle Mariners placed RHP Carlos Vargas on the paternity list. |
| Jul 11 | Tayler Saucedo | Recalled | Seattle Mariners recalled LHP Tayler Saucedo from Tacoma Rainiers. |
| Jul 9 | Jacob Hurtubise | Outrighted | Seattle Mariners sent LF Jacob Hurtubise outright to Tacoma Rainiers. |
| Jul 8 | Angel Chicuate | Signed as Free Agent | Seattle Mariners signed free agent RHP Angel Chicuate to a minor league contract. |
| Jul 5 | Collin Snider | Assigned | Seattle Mariners sent RHP Collin Snider on a rehab assignment to Tacoma Rainiers. |
| Jul 3 | Joe Jacques | Optioned | Seattle Mariners optioned LHP Joe Jacques to Tacoma Rainiers. |
| Jul 3 | Logan Evans | Recalled | Seattle Mariners recalled RHP Logan Evans from Tacoma Rainiers. |
| Jul 2 | Zach Pop | Outrighted | Seattle Mariners sent RHP Zach Pop outright to Tacoma Rainiers. |
| Jul 2 | Emerson Hancock | Optioned | Seattle Mariners optioned RHP Emerson Hancock to Tacoma Rainiers. |
| Jul 2 | Joe Jacques | Selected | Seattle Mariners selected the contract of LHP Joe Jacques from Tacoma Rainiers. |
| Jul 1 | Natanael Garabitos | Signed as Free Agent | Seattle Mariners signed free agent RHP Natanael Garabitos to a minor league contract. |
| Jun 28 | Juan Burgos | Selected | Seattle Mariners selected the contract of RHP Juan Burgos from Tacoma Rainiers. |
| Jun 28 | Zach Pop | Designated for Assignment | Seattle Mariners designated RHP Zach Pop for assignment. |
| Jun 26 | Rowdy Tellez | Released | Seattle Mariners released 1B Rowdy Tellez. |
| Jun 20 | Rowdy Tellez | Designated for Assignment | Seattle Mariners designated 1B Rowdy Tellez for assignment. |
| Jun 20 | Luke Raley | Status Change | Seattle Mariners activated RF Luke Raley from the 10-day injured list. |
| Jun 17 | Jacob Hurtubise | Claimed Off Waivers | Seattle Mariners claimed LF Jacob Hurtubise off waivers from Cincinnati Reds. |
| Jun 16 | Josh Fleming | Signed as Free Agent | Seattle Mariners signed free agent LHP Josh Fleming to a minor league contract. |
| Jun 16 | Jackson Kowar | Optioned | Seattle Mariners optioned RHP Jackson Kowar to Tacoma Rainiers. |
| Jun 16 | Logan Gilbert | Status Change | Seattle Mariners activated RHP Logan Gilbert from the 15-day injured list. |
| Jun 14 | — | Trade | Seattle Mariners traded 3B Nick Dunn to Philadelphia Phillies for cash. |
| Jun 13 | Logan Evans | Optioned | Seattle Mariners optioned RHP Logan Evans to Tacoma Rainiers. |
| Jun 13 | Zach Pop | Selected | Seattle Mariners selected the contract of RHP Zach Pop from Tacoma Rainiers. |
| Jun 13 | Leody Taveras | Outrighted | Seattle Mariners sent CF Leody Taveras outright to Tacoma Rainiers. |
| Jun 13 | Leody Taveras | Outrighted | Seattle Mariners sent CF Leody Taveras outright to Tacoma Rainiers. |
| Jun 12 | Luke Raley | Assigned | Seattle Mariners sent RF Luke Raley on a rehab assignment to Tacoma Rainiers. |
| Jun 12 | Luke Raley | Assigned | Seattle Mariners sent RF Luke Raley on a rehab assignment to Tacoma Rainiers. |
| Jun 10 | Casey Lawrence | Signed as Free Agent | Seattle Mariners signed free agent RHP Casey Lawrence to a minor league contract. |
| Jun 10 | Bryce Miller | Status Change | Seattle Mariners placed RHP Bryce Miller on the 15-day injured list retroactive to June 7, 2025. Right elbow inflammation. |
| Jun 10 | Logan Evans | Recalled | Seattle Mariners recalled RHP Logan Evans from Tacoma Rainiers. |
| Jun 9 | Casey Lawrence | Outrighted | Seattle Mariners sent RHP Casey Lawrence outright to Tacoma Rainiers. |
| Jun 9 | Leody Taveras | Designated for Assignment | Seattle Mariners designated CF Leody Taveras for assignment. |
| Jun 9 | Dominic Canzone | Recalled | Seattle Mariners recalled RF Dominic Canzone from Tacoma Rainiers. |
| Jun 7 | Trevor Gott | Signed as Free Agent | Seattle Mariners signed free agent RHP Trevor Gott to a minor league contract. |
| Jun 7 | Trent Thornton | Status Change | Seattle Mariners activated RHP Trent Thornton from the 15-day injured list. |
| Jun 7 | Casey Lawrence | Designated for Assignment | Seattle Mariners designated RHP Casey Lawrence for assignment. |
| Jun 4 | Collin Snider | Status Change | Seattle Mariners placed RHP Collin Snider on the 15-day injured list. Right forearm flexor strain. |
| Jun 4 | Casey Legumina | Recalled | Seattle Mariners recalled RHP Casey Legumina from Tacoma Rainiers. |
| Jun 3 | Daniel Bard | Signed as Free Agent | Seattle Mariners signed free agent RHP Daniel Bard to a minor league contract. |
| Jun 3 | Jesse Hahn | Signed as Free Agent | Seattle Mariners signed free agent RHP Jesse Hahn to a minor league contract. |
| Jun 2 | Joe Jacques | Trade | Seattle Mariners traded RHP Will Klein to Los Angeles Dodgers for LHP Joe Jacques. |
| Jun 1 | Blake Hunt | Outrighted | Seattle Mariners sent C Blake Hunt outright to Tacoma Rainiers. |
| May 31 | Dalton Davis | Assigned | 1B Dalton Davis assigned to Seattle Mariners. |
| May 31 | Casey Legumina | Optioned | Seattle Mariners optioned RHP Casey Legumina to Tacoma Rainiers. |
| May 31 | Leo Rivas | Optioned | Seattle Mariners optioned 2B Leo Rivas to Tacoma Rainiers. |
| May 31 | Cole Young | Selected | Seattle Mariners selected the contract of SS Cole Young from Tacoma Rainiers. |
| May 31 | Bryce Miller | Status Change | Seattle Mariners activated RHP Bryce Miller from the 15-day injured list. |
| May 31 | Will Klein | Designated for Assignment | Seattle Mariners designated RHP Will Klein for assignment. |
| May 30 | Trent Thornton | Assigned | Seattle Mariners sent RHP Trent Thornton on a rehab assignment to Tacoma Rainiers. |
| May 30 | Trent Thornton | Assigned | Seattle Mariners sent RHP Trent Thornton on a rehab assignment to Tacoma Rainiers. |
| May 29 | Logan Gilbert | Assigned | Seattle Mariners sent RHP Logan Gilbert on a rehab assignment to Tacoma Rainiers. |
| May 29 | Logan Gilbert | Assigned | Seattle Mariners sent RHP Logan Gilbert on a rehab assignment to Tacoma Rainiers. |
| May 29 | Blake Hunt | Designated for Assignment | Seattle Mariners designated C Blake Hunt for assignment. |
| May 29 | Casey Lawrence | Selected | Seattle Mariners selected the contract of RHP Casey Lawrence from ACL Mariners. |
| May 29 | Blas Castaño | Optioned | Seattle Mariners optioned RHP Blas Castaño to Tacoma Rainiers. |
| May 28 | Jackson Kowar | Status Change | Seattle Mariners activated RHP Jackson Kowar from the 60-day injured list. |
| May 28 | Logan Evans | Optioned | Seattle Mariners optioned RHP Logan Evans to Tacoma Rainiers. |
| May 26 | Austin Shenton | Outrighted | Seattle Mariners sent 1B Austin Shenton outright to Tacoma Rainiers. |
| May 26 | Jesse Hahn | Outrighted | Seattle Mariners sent RHP Jesse Hahn outright to Tacoma Rainiers. |
| May 24 | Casey Lawrence | Signed as Free Agent | Seattle Mariners signed free agent RHP Casey Lawrence to a minor league contract. |
| May 23 | Jesse Hahn | Designated for Assignment | Seattle Mariners designated RHP Jesse Hahn for assignment. |
| May 23 | Blas Castaño | Recalled | Seattle Mariners recalled RHP Blas Castano from Tacoma Rainiers. |
| May 23 | Casey Lawrence | Outrighted | Seattle Mariners sent RHP Casey Lawrence outright to Tacoma Rainiers. |
| May 22 | George Kirby | Status Change | Seattle Mariners activated RHP George Kirby from the 15-day injured list. |
| May 22 | Troy Taylor | Optioned | Seattle Mariners optioned RHP Troy Taylor to Tacoma Rainiers. |
| May 21 | Jesse Hahn | Status Change | Seattle Mariners activated RHP Jesse Hahn. |
| May 21 | Jesse Hahn | Selected | Seattle Mariners selected the contract of RHP Jesse Hahn from Tacoma Rainiers. |
| May 21 | Casey Lawrence | Designated for Assignment | Seattle Mariners designated RHP Casey Lawrence for assignment. |
| May 20 | Casey Lawrence | Selected | Seattle Mariners selected the contract of RHP Casey Lawrence from Tacoma Rainiers. |
| May 20 | Jhonathan Díaz | Optioned | Seattle Mariners optioned LHP Jhonathan Díaz to Tacoma Rainiers. |
| May 20 | Austin Shenton | Designated for Assignment | Seattle Mariners designated 1B Austin Shenton for assignment. |
| May 14 | Bryce Miller | Status Change | Seattle Mariners placed RHP Bryce Miller on the 15-day injured list retroactive to May 12, 2025. Right elbow inflammation. |
| May 14 | Jhonathan Díaz | Recalled | Seattle Mariners recalled LHP Jhonathan Díaz from Tacoma Rainiers. |
| May 13 | Tomo Otosaka | Signed as Free Agent | Seattle Mariners signed free agent OF Tomo Otosaka to a minor league contract. |
| May 10 | Jackson Kowar | Assigned | Seattle Mariners sent RHP Jackson Kowar on a rehab assignment to Tacoma Rainiers. |
| May 9 | Troy Taylor | Recalled | Seattle Mariners recalled RHP Troy Taylor from Tacoma Rainiers. |
| May 9 | Trent Thornton | Status Change | Seattle Mariners placed RHP Trent Thornton on the 15-day injured list retroactive to May 6, 2025. Appendicitis. |
| May 8 | Luis F. Castillo | Trade | Seattle Mariners traded RHP Luis F. Castillo to Baltimore Orioles for cash. |
| May 7 | Casey Lawrence | Signed as Free Agent | Seattle Mariners signed free agent RHP Casey Lawrence to a minor league contract. |
| May 7 | Rhylan Thomas | Optioned | Seattle Mariners optioned LF Rhylan Thomas to Tacoma Rainiers. |
| May 7 | Leody Taveras | Status Change | Seattle Mariners activated CF Leody Taveras. |
| May 6 | Luis F. Castillo | Designated for Assignment | Seattle Mariners designated RHP Luis F. Castillo for assignment. |
| May 6 | Leody Taveras | Claimed Off Waivers | Seattle Mariners claimed CF Leody Taveras off waivers from Texas Rangers. |
| May 6 | Luis F. Castillo | Designated for Assignment | Seattle Mariners designated RHP Luis F. Castillo for assignment. |
| May 6 | Dylan Moore | Status Change | Seattle Mariners activated 3B Dylan Moore from the 10-day injured list. |
| May 6 | Samad Taylor | Optioned | Seattle Mariners optioned 2B Samad Taylor to Tacoma Rainiers. |
| May 4 | George Kirby | Assigned | Seattle Mariners sent RHP George Kirby on a rehab assignment to Tacoma Rainiers. |
| May 3 | Jackson Kowar | Assigned | Seattle Mariners sent RHP Jackson Kowar on a rehab assignment to ACL Mariners. |
| May 3 | Jackson Kowar | Assigned | Seattle Mariners sent RHP Jackson Kowar on a rehab assignment to ACL Mariners. |
| May 3 | Troy Taylor | Optioned | Seattle Mariners optioned RHP Troy Taylor to Tacoma Rainiers. |
| May 3 | Matt Brash | Status Change | Seattle Mariners activated RHP Matt Brash from the 15-day injured list. |
| May 2 | Sauryn Lao | Outrighted | Seattle Mariners sent RHP Sauryn Lao outright to Tacoma Rainiers. |
| Apr 30 | Noah Manning | Signed as Free Agent | Seattle Mariners signed free agent RHP Noah Manning to a minor league contract. |
| Apr 30 | Jacob Denner | Signed as Free Agent | Seattle Mariners signed free agent LHP Jacob Denner to a minor league contract. |
| Apr 30 | Luke Raley | Status Change | Seattle Mariners placed RF Luke Raley on the 10-day injured list retroactive to April 28, 2025. Right oblique strain. |
| Apr 30 | Sauryn Lao | Designated for Assignment | Seattle Mariners designated RHP Sauryn Lao for assignment. |
| Apr 30 | Rhylan Thomas | Selected | Seattle Mariners selected the contract of LF Rhylan Thomas from Tacoma Rainiers. |
| Apr 29 | Bryan Shaw | Signed as Free Agent | Seattle Mariners signed free agent RHP Bryan Shaw to a minor league contract. |
| Apr 29 | Gregory Santos | Status Change | Seattle Mariners placed RHP Gregory Santos on the 60-day injured list. |
| Apr 29 | Samad Taylor | Selected | Seattle Mariners selected the contract of 2B Samad Taylor from Tacoma Rainiers. |
| Apr 28 | Casey Lawrence | Claimed Off Waivers | Toronto Blue Jays claimed RHP Casey Lawrence off waivers from Seattle Mariners. |
| Apr 27 | Tayler Saucedo | Optioned | Seattle Mariners optioned LHP Tayler Saucedo to Tacoma Rainiers. |
| Apr 27 | Logan Evans | Selected | Seattle Mariners selected the contract of RHP Logan Evans from Tacoma Rainiers. |
| Apr 26 | Andrew Carson | Signed as Free Agent | Seattle Mariners signed free agent RHP Andrew Carson to a minor league contract. |
| Apr 26 | Troy Taylor | Recalled | Seattle Mariners recalled RHP Troy Taylor from Tacoma Rainiers. |
| Apr 26 | Tayler Saucedo | Recalled | Seattle Mariners recalled LHP Tayler Saucedo from Tacoma Rainiers. |
| Apr 26 | Casey Lawrence | Designated for Assignment | Seattle Mariners designated RHP Casey Lawrence for assignment. |
| Apr 26 | Logan Gilbert | Status Change | Seattle Mariners placed RHP Logan Gilbert on the 15-day injured list. Right elbow flexor strain. |
| Apr 23 | Casey Lawrence | Selected | Seattle Mariners selected the contract of RHP Casey Lawrence from Tacoma Rainiers. |
| Apr 23 | Sauryn Lao | Optioned | Seattle Mariners optioned RHP Sauryn Lao to Tacoma Rainiers. |
| Apr 23 | Victor Robles | Status Change | Seattle Mariners transferred RF Victor Robles from the 10-day injured list to the 60-day injured list. |
| Apr 22 | Casey Lawrence | Outrighted | Seattle Mariners sent RHP Casey Lawrence outright to Tacoma Rainiers. |
| Apr 21 | Drew Pomeranz | Trade | Seattle Mariners traded LHP Drew Pomeranz to Chicago Cubs. |
| Apr 20 | Casey Lawrence | Designated for Assignment | Seattle Mariners designated RHP Casey Lawrence for assignment. |
| Apr 20 | Sauryn Lao | Selected | Seattle Mariners selected the contract of RHP Sauryn Lao from Tacoma Rainiers. |
| Apr 18 | Casey Lawrence | Selected | Seattle Mariners selected the contract of RHP Casey Lawrence from Tacoma Rainiers. |
| Apr 18 | Troy Taylor | Optioned | Seattle Mariners optioned RHP Troy Taylor to Tacoma Rainiers. |
| Apr 17 | Casey Lawrence | Signed as Free Agent | Seattle Mariners signed free agent RHP Casey Lawrence to a minor league contract. |
| Apr 17 | Emerson Hancock | Recalled | Seattle Mariners recalled RHP Emerson Hancock from Tacoma Rainiers. |
| Apr 17 | Will Klein | Optioned | Seattle Mariners optioned RHP Will Klein to Tacoma Rainiers. |
| Apr 16 | Randy Arozarena | Status Change | Seattle Mariners activated LF Randy Arozarena. |
| Apr 16 | Zach Pop | Signed as Free Agent | Seattle Mariners signed free agent RHP Zach Pop to a minor league contract. |
| Apr 16 | Casey Lawrence | Declared Free Agency | RHP Casey Lawrence elected free agency. |
| Apr 16 | Gregory Santos | Optioned | Seattle Mariners optioned RHP Gregory Santos to Tacoma Rainiers. |
| Apr 16 | Will Klein | Recalled | Seattle Mariners recalled RHP Will Klein from Tacoma Rainiers. |
| Apr 16 | Andrés Muñoz | Number Change | RHP Andrés Muñoz changed number to 75. |
| Apr 16 | J.P. Crawford | Number Change | SS J.P. Crawford changed number to 3. |
| Apr 16 | Dylan Moore | Number Change | SS Dylan Moore changed number to 25. |
| Apr 16 | Logan Gilbert | Number Change | RHP Logan Gilbert changed number to 36. |
| Apr 16 | Cal Raleigh | Number Change | C Cal Raleigh changed number to 29. |
| Apr 16 | Gabe Speier | Number Change | LHP Gabe Speier changed number to 55. |
| Apr 16 | Luis Castillo | Number Change | RHP Luis Castillo changed number to 58. |
| Apr 16 | Julio Rodríguez | Number Change | CF Julio Rodríguez changed number to 44. |
| Apr 16 | Carlos Vargas | Number Change | RHP Carlos Vargas changed number to 54. |
| Apr 16 | Bryce Miller | Number Change | RHP Bryce Miller changed number to 50. |
| Apr 16 | Bryan Woo | Number Change | RHP Bryan Woo changed number to 22. |
| Apr 16 | Eduard Bazardo | Number Change | RHP Eduard Bazardo changed number to 83. |
| Apr 16 | Mitch Garver | Number Change | C Mitch Garver changed number to 18. |
| Apr 16 | Luke Raley | Number Change | LF Luke Raley changed number to 20. |
| Apr 16 | Randy Arozarena | Number Change | LF Randy Arozarena changed number to 56. |
| Apr 16 | Leo Rivas | Number Change | SS Leo Rivas changed number to 76. |
| Apr 16 | Collin Snider | Number Change | RHP Collin Snider changed number to 52. |
| Apr 16 | Gregory Santos | Number Change | RHP Gregory Santos changed number to 48. |
| Apr 16 | Trent Thornton | Number Change | RHP Trent Thornton changed number to 46. |
| Apr 16 | Troy Taylor | Number Change | RHP Troy Taylor changed number to 59. |
| Apr 16 | Casey Legumina | Number Change | RHP Casey Legumina changed number to 64. |
| Apr 16 | Miles Mastrobuoni | Number Change | SS Miles Mastrobuoni changed number to 21. |
| Apr 16 | Donovan Solano | Number Change | 3B Donovan Solano changed number to 39. |
| Apr 16 | Rowdy Tellez | Number Change | 1B Rowdy Tellez changed number to 23. |
| Apr 16 | Jorge Polanco | Number Change | 2B Jorge Polanco changed number to 7. |
| Apr 16 | Ben Williamson | Number Change | 3B Ben Williamson changed number to 9. |
| Apr 15 | Jesse Hahn | Signed as Free Agent | Seattle Mariners signed free agent RHP Jesse Hahn to a minor league contract. |
| Apr 15 | Andrés Muñoz | Number Change | RHP Andrés Muñoz changed number to 42. |
| Apr 15 | Dylan Moore | Number Change | SS Dylan Moore changed number to 42. |
| Apr 15 | J.P. Crawford | Number Change | SS J.P. Crawford changed number to 42. |
| Apr 15 | Cal Raleigh | Number Change | C Cal Raleigh changed number to 42. |
| Apr 15 | Gabe Speier | Number Change | LHP Gabe Speier changed number to 42. |
| Apr 15 | Luis Castillo | Number Change | RHP Luis Castillo changed number to 42. |
| Apr 15 | Julio Rodríguez | Number Change | CF Julio Rodríguez changed number to 42. |
| Apr 15 | Bryce Miller | Number Change | RHP Bryce Miller changed number to 42. |
| Apr 15 | Logan Gilbert | Number Change | RHP Logan Gilbert changed number to 42. |
| Apr 15 | Mitch Garver | Number Change | C Mitch Garver changed number to 42. |
| Apr 15 | Carlos Vargas | Number Change | RHP Carlos Vargas changed number to 42. |
| Apr 15 | Bryan Woo | Number Change | RHP Bryan Woo changed number to 42. |
| Apr 15 | Trent Thornton | Number Change | RHP Trent Thornton changed number to 42. |
| Apr 15 | Eduard Bazardo | Number Change | RHP Eduard Bazardo changed number to 42. |
| Apr 15 | Luke Raley | Number Change | LF Luke Raley changed number to 42. |
| Apr 15 | Randy Arozarena | Number Change | LF Randy Arozarena changed number to 42. |
| Apr 15 | Troy Taylor | Number Change | RHP Troy Taylor changed number to 42. |
| Apr 15 | Leo Rivas | Number Change | SS Leo Rivas changed number to 42. |
| Apr 15 | Gregory Santos | Number Change | RHP Gregory Santos changed number to 42. |
| Apr 15 | Jorge Polanco | Number Change | 2B Jorge Polanco changed number to 42. |
| Apr 15 | Collin Snider | Number Change | RHP Collin Snider changed number to 42. |
| Apr 15 | Rowdy Tellez | Number Change | 1B Rowdy Tellez changed number to 42. |
| Apr 15 | Donovan Solano | Number Change | 3B Donovan Solano changed number to 42. |
| Apr 15 | Miles Mastrobuoni | Number Change | SS Miles Mastrobuoni changed number to 42. |
| Apr 15 | Ben Williamson | Number Change | 3B Ben Williamson changed number to 42. |
| Apr 15 | Casey Legumina | Number Change | RHP Casey Legumina changed number to 42. |
| Apr 14 | Justin Sanchez | Signed as Free Agent | Seattle Mariners signed free agent LHP Justin Sanchez to a minor league contract. |
| Apr 14 | Troy Taylor | Status Change | Seattle Mariners activated RHP Troy Taylor from the 15-day injured list. |
| Apr 14 | Casey Lawrence | Designated for Assignment | Seattle Mariners designated RHP Casey Lawrence for assignment. |
| Apr 13 | Matt Brash | Assigned | Seattle Mariners sent RHP Matt Brash on a rehab assignment to Tacoma Rainiers. |
| Apr 13 | Ben Williamson | Selected | Seattle Mariners selected the contract of 3B Ben Williamson from Tacoma Rainiers. |
| Apr 13 | Dominic Canzone | Optioned | Seattle Mariners optioned RF Dominic Canzone to Tacoma Rainiers. |
| Apr 13 | Ryan Bliss | Status Change | Seattle Mariners transferred 2B Ryan Bliss from the 10-day injured list to the 60-day injured list. Torn left biceps. |
| Apr 12 | Jesse Hahn | Outrighted | Seattle Mariners sent RHP Jesse Hahn outright to Tacoma Rainiers. |
| Apr 11 | Diego Contreras | Signed as Free Agent | Seattle Mariners signed free agent IF Diego Contreras to a minor league contract. |
| Apr 11 | Osvaldo Platas | Signed as Free Agent | Seattle Mariners signed free agent RHP Osvaldo Platas to a minor league contract. |
| Apr 11 | Kevin Pino | Signed as Free Agent | Seattle Mariners signed free agent RHP Kevin Pino to a minor league contract. |
| Apr 11 | Michael Mariot | Signed as Free Agent | Seattle Mariners signed free agent RHP Michael Mariot to a minor league contract. |
| Apr 11 | Casey Legumina | Recalled | Seattle Mariners recalled RHP Casey Legumina from Tacoma Rainiers. |
| Apr 10 | Luis F. Castillo | Optioned | Seattle Mariners optioned RHP Luis F. Castillo to Tacoma Rainiers. |
| Apr 9 | Jesse Hahn | Designated for Assignment | Seattle Mariners designated RHP Jesse Hahn for assignment. |
| Apr 9 | Ryan Bliss | Status Change | Seattle Mariners placed 2B Ryan Bliss on the 10-day injured list. Left biceps tear. |
| Apr 9 | Leo Rivas | Recalled | Seattle Mariners recalled SS Leo Rivas from Tacoma Rainiers. |
| Apr 9 | Casey Lawrence | Selected | Seattle Mariners selected the contract of RHP Casey Lawrence from Tacoma Rainiers. |
| Apr 8 | Cody Bolton | Trade | Seattle Mariners traded RHP Cody Bolton to Cleveland Guardians for cash. |
| Apr 7 | Victor Robles | Status Change | Seattle Mariners placed CF Victor Robles on the 10-day injured list. Left shoulder dislocation. |
| Apr 7 | Dominic Canzone | Recalled | Seattle Mariners recalled RF Dominic Canzone from Tacoma Rainiers. |
| Apr 7 | Hagen Danner | Outrighted | Seattle Mariners sent RHP Hagen Danner outright to Tacoma Rainiers. |
| Apr 5 | Jesse Hahn | Selected | Seattle Mariners selected the contract of RHP Jesse Hahn from Tacoma Rainiers. |
| Apr 5 | Tayler Saucedo | Optioned | Seattle Mariners optioned LHP Tayler Saucedo to Tacoma Rainiers. |
| Apr 5 | Cody Bolton | Designated for Assignment | Seattle Mariners designated RHP Cody Bolton for assignment. |
| Apr 4 | Luis F. Castillo | Selected | Seattle Mariners selected the contract of RHP Luis F. Castillo from Tacoma Rainiers. |
| Apr 4 | Hagen Danner | Designated for Assignment | Seattle Mariners designated RHP Hagen Danner for assignment. |
| Apr 3 | Jhonathan Díaz | Optioned | Seattle Mariners optioned LHP Jhonathan Díaz to Tacoma Rainiers. |
| Apr 3 | Leo Rivas | Optioned | Seattle Mariners optioned SS Leo Rivas to Tacoma Rainiers. |
| Apr 3 | Jorge Polanco | Status Change | Seattle Mariners activated 2B Jorge Polanco from the paternity list. |
| Apr 1 | Leo Rivas | Recalled | Seattle Mariners recalled SS Leo Rivas from Tacoma Rainiers. |
| Apr 1 | Jorge Polanco | Status Change | Seattle Mariners placed 2B Jorge Polanco on the paternity list. |
| Apr 1 | Emerson Hancock | Optioned | Seattle Mariners optioned RHP Emerson Hancock to Tacoma Rainiers. |
| Apr 1 | Jhonathan Díaz | Selected | Seattle Mariners selected the contract of LHP Jhonathan Díaz from Tacoma Rainiers. |
| Apr 1 | Troy Taylor | Assigned | Seattle Mariners sent RHP Troy Taylor on a rehab assignment to Tacoma Rainiers. |
| Apr 1 | William Fleming | Signed as Free Agent | Seattle Mariners signed free agent RHP William Fleming to a minor league contract. |
| Mar 29 | Nick Fraze | Signed as Free Agent | Seattle Mariners signed free agent RHP Nick Fraze to a minor league contract. |
| Mar 28 | Nico Tellache | Signed as Free Agent | Seattle Mariners signed free agent LHP Nico Tellache to a minor league contract. |
| Mar 27 | Ben Hernandez | Signed as Free Agent | Seattle Mariners signed free agent RHP Ben Hernandez to a minor league contract. |
| Mar 27 | Drew Pomeranz | Signed as Free Agent | Seattle Mariners signed free agent LHP Drew Pomeranz to a minor league contract. |
| Mar 27 | Jesse Hahn | Signed as Free Agent | Seattle Mariners signed free agent RHP Jesse Hahn to a minor league contract. |
| Mar 27 | Troy Taylor | Status Change | Seattle Mariners placed RHP Troy Taylor on the 15-day injured list retroactive to March 24, 2025. Right lat strain. |
| Mar 27 | George Kirby | Status Change | Seattle Mariners placed RHP George Kirby on the 15-day injured list retroactive to March 24, 2025. Right shoulder inflammation. |
| Mar 27 | Matt Brash | Status Change | Seattle Mariners placed RHP Matt Brash on the 15-day injured list retroactive to March 24, 2025. Right UCL sprain. |
| Mar 25 | Rowdy Tellez | Status Change | Seattle Mariners activated 1B Rowdy Tellez. |
| Mar 25 | Rowdy Tellez | Selected | Seattle Mariners selected the contract of 1B Rowdy Tellez from Tacoma Rainiers. |
| Mar 24 | Andruw Salcedo | Assigned | C Andruw Salcedo assigned to Seattle Mariners. |
| Mar 24 | Kelvin Alcantara | Assigned | CF Kelvin Alcantara assigned to Seattle Mariners. |
| Mar 24 | Gabriel Moncada | Assigned | 1B Gabriel Moncada assigned to Seattle Mariners. |
| Mar 23 | Leo Rivas | Optioned | Seattle Mariners optioned SS Leo Rivas to Tacoma Rainiers. |
| Mar 23 | Blake Hunt | Optioned | Seattle Mariners optioned C Blake Hunt to Tacoma Rainiers. |
| Mar 23 | Casey Legumina | Optioned | Seattle Mariners optioned RHP Casey Legumina to Tacoma Rainiers. |
| Mar 23 | Mitch Haniger | Released | Seattle Mariners released RF Mitch Haniger. |
| Mar 22 | Michael Hobbs | Trade | New York Mets traded RHP Michael Hobbs to Seattle Mariners. |
| Mar 22 | Dominic Canzone | Optioned | Seattle Mariners optioned RF Dominic Canzone to Tacoma Rainiers. |
| Mar 22 | Austin Shenton | Optioned | Seattle Mariners optioned 1B Austin Shenton to Tacoma Rainiers. |
| Mar 22 | Allan Saathoff | Assigned | RHP Allan Saathoff assigned to Seattle Mariners. |
| Mar 21 | Calvin Schapira | Signed as Free Agent | Seattle Mariners signed free agent LHP Calvin Schapira to a minor league contract. |
| Mar 21 | Ricardo Cova | Assigned | 2B Ricardo Cova assigned to Seattle Mariners. |
| Mar 18 | George Feliz | Assigned | CF George Feliz assigned to Seattle Mariners. |
| Mar 16 | Yoyner Fajardo | Assigned | OF Yoyner Fajardo assigned to Seattle Mariners. |
| Mar 16 | Cesar Quintas | Assigned | CF Cesar Quintas assigned to Seattle Mariners. |
| Mar 16 | Hunter Fitz-Gerald | Assigned | 1B Hunter Fitz-Gerald assigned to Seattle Mariners. |
| Mar 16 | Dervy Ventura | Assigned | 2B Dervy Ventura assigned to Seattle Mariners. |
| Mar 16 | Jordan Jackson | Assigned | RHP Jordan Jackson assigned to Seattle Mariners. |
| Mar 16 | Kyle Hill | Assigned | RHP Kyle Hill assigned to Seattle Mariners. |
| Mar 15 | Seth Martinez | Claimed Off Waivers | Miami Marlins claimed RHP Seth Martinez off waivers from Seattle Mariners. |
| Mar 15 | Adrian Quintana | Assigned | RHP Adrian Quintana assigned to Seattle Mariners. |
| Mar 15 | Matthew Ellis | Assigned | C Matthew Ellis assigned to Seattle Mariners. |
| Mar 15 | Matt Cronin | Assigned | LHP Matt Cronin assigned to Seattle Mariners. |
| Mar 15 | Jean Munoz | Assigned | RHP Jean Munoz assigned to Seattle Mariners. |
| Mar 15 | Victor Labrada | Assigned | CF Victor Labrada assigned to Seattle Mariners. |
| Mar 15 | Tyler Locklear | Optioned | Seattle Mariners optioned 1B Tyler Locklear to Tacoma Rainiers. |
| Mar 14 | Neftalí Feliz | Released | Seattle Mariners released RHP Neftalí Feliz. |
| Mar 14 | Will Klein | Optioned | Seattle Mariners optioned RHP Will Klein to Tacoma Rainiers. |
| Mar 14 | Anyelo Ovando | Assigned | RHP Anyelo Ovando assigned to Seattle Mariners. |
| Mar 14 | Ryan Picollo | Assigned | OF Ryan Picollo assigned to Seattle Mariners. |
| Mar 13 | Austin St. Laurent | Assigned | 3B Austin St. Laurent assigned to Seattle Mariners. |
| Mar 13 | Julio E. Rodriguez | Assigned | C Julio E. Rodriguez assigned to Seattle Mariners. |
| Mar 12 | Colin Davis | Assigned | LF Colin Davis assigned to Seattle Mariners. |
| Mar 12 | Ben Ramirez | Assigned | 3B Ben Ramirez assigned to Seattle Mariners. |
| Mar 10 | Cody Bolton | Optioned | Seattle Mariners optioned RHP Cody Bolton to Tacoma Rainiers. |
| Mar 8 | Curtis Washington Jr. | Assigned | CF Curtis Washington Jr. assigned to Seattle Mariners. |
| Mar 8 | Reid Morgan | Assigned | RHP Reid Morgan assigned to Seattle Mariners. |
| Mar 8 | Axel Sanchez | Assigned | SS Axel Sanchez assigned to Seattle Mariners. |
| Mar 7 | Blas Castaño | Optioned | Seattle Mariners optioned RHP Blas Castano to Tacoma Rainiers. |
| Mar 7 | Hagen Danner | Optioned | Seattle Mariners optioned RHP Hagen Danner to Tacoma Rainiers. |
| Mar 6 | Travis Kuhn | Assigned | RHP Travis Kuhn assigned to Seattle Mariners. |
| Mar 2 | Seth Martinez | Claimed Off Waivers | Seattle Mariners claimed RHP Seth Martinez off waivers from Miami Marlins. |
| Mar 2 | Jackson Kowar | Status Change | Seattle Mariners placed RHP Jackson Kowar on the 60-day injured list. Tommy John surgery recovery. |
| Mar 2 | Dauris Valdez | Released | Seattle Mariners released RHP Dauris Valdez. |
| Feb 28 | Andrew Miller | Assigned | C Andrew Miller assigned to Seattle Mariners. |
| Feb 27 | Jose Caguana | Assigned | C Jose Caguana assigned to Seattle Mariners. |
| Feb 27 | Anthony Donofrio | Assigned | OF Anthony Donofrio assigned to Seattle Mariners. |
| Feb 27 | Felnin Celesten | Assigned | SS Felnin Celesten assigned to Seattle Mariners. |
| Feb 27 | Ryan Hawks | Assigned | RHP Ryan Hawks assigned to Seattle Mariners. |
| Feb 27 | Jack White | Assigned | LHP Jack White assigned to Seattle Mariners. |
| Feb 27 | Connor Dykstra | Assigned | C Connor Dykstra assigned to Seattle Mariners. |
| Feb 27 | Danny Wirchansky | Assigned | LHP Danny Wirchansky assigned to Seattle Mariners. |
| Feb 27 | Evan Truitt | Assigned | RHP Evan Truitt assigned to Seattle Mariners. |
| Feb 27 | Dylan File | Assigned | RHP Dylan File assigned to Seattle Mariners. |
| Feb 27 | Gabriel Sosa | Assigned | RHP Gabriel Sosa assigned to Seattle Mariners. |
| Feb 27 | Josh Hood | Assigned | 2B Josh Hood assigned to Seattle Mariners. |
| Feb 26 | Carson Jones | Assigned | LF Carson Jones assigned to Seattle Mariners. |
| Feb 25 | Blake Rambusch | Assigned | 2B Blake Rambusch assigned to Seattle Mariners. |
| Feb 25 | Caleb Cali | Assigned | 3B Caleb Cali assigned to Seattle Mariners. |
| Feb 25 | Gage Boehm | Assigned | RHP Gage Boehm assigned to Seattle Mariners. |
| Feb 25 | Brock Moore | Assigned | RHP Brock Moore assigned to Seattle Mariners. |
| Feb 25 | Harrison Kreiling | Assigned | RHP Harrison Kreiling assigned to Seattle Mariners. |
| Feb 25 | Yorlin Calderon | Assigned | RHP Yorlin Calderon assigned to Seattle Mariners. |
| Feb 25 | Trevor Gott | Signed as Free Agent | Seattle Mariners signed free agent RHP Trevor Gott to a minor league contract and invited him to spring training. |
| Feb 24 | Milkar Perez | Assigned | 3B Milkar Perez assigned to Seattle Mariners. |
| Feb 24 | Jason Ruffcorn | Assigned | RHP Jason Ruffcorn assigned to Seattle Mariners. |
| Feb 24 | Elijah Dale | Assigned | RHP Elijah Dale assigned to Seattle Mariners. |
| Feb 23 | Christian Little | Assigned | RHP Christian Little assigned to Seattle Mariners. |
| Feb 23 | Luis Suisbel | Assigned | 1B Luis Suisbel assigned to Seattle Mariners. |
| Feb 23 | Brandon Eike | Assigned | 3B Brandon Eike assigned to Seattle Mariners. |
| Feb 23 | Stefan Raeth | Assigned | RHP Stefan Raeth assigned to Seattle Mariners. |
| Feb 22 | Tai Peete | Assigned | 3B Tai Peete assigned to Seattle Mariners. |
| Feb 22 | Jared Sundstrom | Assigned | OF Jared Sundstrom assigned to Seattle Mariners. |
| Feb 22 | Carlos Jimenez | Assigned | CF Carlos Jimenez assigned to Seattle Mariners. |
| Feb 22 | Charlie Pagliarini | Assigned | 3B Charlie Pagliarini assigned to Seattle Mariners. |
| Feb 22 | Jack López | Assigned | 2B Jack López assigned to Seattle Mariners. |
| Feb 22 | Jesse Wainscott | Assigned | RHP Jesse Wainscott assigned to Seattle Mariners. |
| Feb 22 | Wyatt Lunsford-Shenkman | Assigned | RHP Wyatt Lunsford-Shenkman assigned to Seattle Mariners. |
| Feb 22 | Charlie Beilenson | Assigned | RHP Charlie Beilenson assigned to Seattle Mariners. |
| Feb 22 | Taylor Floyd | Assigned | RHP Taylor Floyd assigned to Seattle Mariners. |
| Feb 22 | Jimmy Joyce | Assigned | RHP Jimmy Joyce assigned to Seattle Mariners. |
| Feb 22 | Juan Burgos | Assigned | RHP Juan Burgos assigned to Seattle Mariners. |
| Feb 21 | Jimmy Kingsbury | Assigned | RHP Jimmy Kingsbury assigned to Seattle Mariners. |
| Feb 21 | Hogan Windish | Assigned | 1B Hogan Windish assigned to Seattle Mariners. |
| Feb 21 | Bill Knight | Assigned | OF Bill Knight assigned to Seattle Mariners. |
| Feb 21 | Rowdy Tellez | Signed as Free Agent | Seattle Mariners signed free agent 1B Rowdy Tellez to a minor league contract and invited him to spring training. |
| Feb 19 | Kleiver Benitez | Signed as Free Agent | Seattle Mariners signed free agent RHP Kleiver Benitez to a minor league contract. |
| Feb 15 | Garrett Hill | Signed as Free Agent | Seattle Mariners signed free agent RHP Garrett Hill to a minor league contract. |
| Feb 15 | Jhonathan Díaz | Signed as Free Agent | Seattle Mariners signed free agent LHP Jhonathan Díaz to a minor league contract and invited him to spring training. |
| Feb 7 | Jhonathan Díaz | Declared Free Agency | LHP Jhonathan Díaz elected free agency. |
| Feb 7 | Cade Marlowe | Outrighted | Seattle Mariners sent LF Cade Marlowe outright to Tacoma Rainiers. |
| Feb 3 | Jhonathan Díaz | Designated for Assignment | Seattle Mariners designated LHP Jhonathan Díaz for assignment. |
| Feb 3 | — | Trade | Cincinnati Reds traded RHP Casey Legumina to Seattle Mariners for cash. |
| Feb 3 | Jorge Polanco | Signed as Free Agent | Seattle Mariners signed free agent 2B Jorge Polanco. |
| Feb 3 | Cade Marlowe | Designated for Assignment | Seattle Mariners designated LF Cade Marlowe for assignment. |
| Jan 30 | Luis F. Castillo | Status Change | RHP Luis F. Castillo roster status changed by Seattle Mariners. |
| Jan 30 | Cole Young | Assigned | Seattle Mariners invited non-roster SS Cole Young to spring training. |
| Jan 30 | Ben Williamson | Assigned | Seattle Mariners invited non-roster 3B Ben Williamson to spring training. |
| Jan 30 | Rhylan Thomas | Assigned | Seattle Mariners invited non-roster LF Rhylan Thomas to spring training. |
| Jan 30 | Samad Taylor | Assigned | Seattle Mariners invited non-roster 2B Samad Taylor to spring training. |
| Jan 30 | Brock Rodden | Assigned | Seattle Mariners invited non-roster 2B Brock Rodden to spring training. |
| Jan 30 | Spencer Packard | Assigned | Seattle Mariners invited non-roster LF Spencer Packard to spring training. |
| Jan 30 | Lazaro Montes | Assigned | Seattle Mariners invited non-roster RF Lazaro Montes to spring training. |
| Jan 30 | Harry Ford | Assigned | Seattle Mariners invited non-roster C Harry Ford to spring training. |
| Jan 30 | Colt Emerson | Assigned | Seattle Mariners invited non-roster SS Colt Emerson to spring training. |
| Jan 30 | Nick Dunn | Assigned | Seattle Mariners invited non-roster 3B Nick Dunn to spring training. |
| Jan 30 | Connor Charping | Assigned | Seattle Mariners invited non-roster C Connor Charping to spring training. |
| Jan 30 | Josh Caron | Assigned | Seattle Mariners invited non-roster C Josh Caron to spring training. |
| Jan 30 | Michael Arroyo | Assigned | Seattle Mariners invited non-roster SS Michael Arroyo to spring training. |
| Jan 30 | Brandyn Garcia | Assigned | Seattle Mariners invited non-roster LHP Brandyn Garcia to spring training. |
| Jan 30 | Shintaro Fujinami | Signed as Free Agent | Seattle Mariners signed free agent RHP Shintaro Fujinami to a minor league contract and invited him to spring training. |
| Jan 30 | Neftalí Feliz | Signed as Free Agent | Seattle Mariners signed free agent RHP Neftalí Feliz to a minor league contract and invited him to spring training. |
| Jan 30 | Logan Evans | Assigned | Seattle Mariners invited non-roster RHP Logan Evans to spring training. |
| Jan 30 | Hunter Cranton | Assigned | Seattle Mariners invited non-roster RHP Hunter Cranton to spring training. |
| Jan 30 | Tyler Cleveland | Assigned | Seattle Mariners invited non-roster RHP Tyler Cleveland to spring training. |
| Jan 30 | Luis F. Castillo | Signed as Free Agent | Seattle Mariners signed free agent RHP Luis Castillo to a minor league contract and invited him to spring training. |
| Jan 30 | Peyton Alford | Assigned | Seattle Mariners invited non-roster LHP Peyton Alford to spring training. |
| Jan 29 | Adam Seminaris | Signed as Free Agent | Seattle Mariners signed free agent LHP Adam Seminaris to a minor league contract. |
| Jan 29 | Diago Machado | Signed as Free Agent | Seattle Mariners signed free agent OF Diago Machado to a minor league contract. |
| Jan 29 | Tyler Jay | Outrighted | Seattle Mariners sent LHP Tyler Jay outright to Tacoma Rainiers. |
| Jan 28 | Nathan Rose | Signed as Free Agent | Seattle Mariners signed free agent SS Nathan Rose to a minor league contract. |
| Jan 22 | Julio E. Rodriguez | Signed as Free Agent | Seattle Mariners signed free agent C Julio E. Rodriguez to a minor league contract. |
| Jan 21 | Samad Taylor | Outrighted | Seattle Mariners sent 2B Samad Taylor outright to Tacoma Rainiers. |
| Jan 21 | Tyler Jay | Designated for Assignment | Seattle Mariners designated LHP Tyler Jay for assignment. |
| Jan 21 | — | Trade | Athletics traded RHP Will Klein to Seattle Mariners for Other Considerations. |
| Jan 21 | Po-Chun Lin | Signed as Free Agent | Seattle Mariners signed free agent 2B Po-Chun Lin to a minor league contract. |
| Jan 17 | Maximo Rodriguez | Signed as Free Agent | Seattle Mariners signed free agent RHP Maximo Rodriguez to a minor league contract. |
| Jan 17 | Nick Raposo | Outrighted | Seattle Mariners sent C Nick Raposo outright to Tacoma Rainiers. |
| Jan 17 | Samad Taylor | Designated for Assignment | Seattle Mariners designated 2B Samad Taylor for assignment. |
| Jan 16 | Alan Carpinteiro | Signed as Free Agent | Seattle Mariners signed free agent RHP Alan Carpinteiro to a minor league contract. |
| Jan 16 | Austin Kitchen | Outrighted | Seattle Mariners sent LHP Austin Kitchen outright to Tacoma Rainiers. |
| Jan 15 | Beau Taylor | Signed as Free Agent | Seattle Mariners signed free agent C Beau Taylor to a minor league contract. |
| Jan 15 | Maikol Rodriguez | Signed as Free Agent | Seattle Mariners signed free agent OF Maikol Rodriguez to a minor league contract. |
| Jan 15 | Randal Munoz | Signed as Free Agent | Seattle Mariners signed free agent RHP Randal Munoz to a minor league contract. |
| Jan 15 | Elias Perez | Signed as Free Agent | Seattle Mariners signed free agent OF Elias Perez to a minor league contract. |
| Jan 15 | Ismanuel Piña | Signed as Free Agent | Seattle Mariners signed free agent RHP Ismanuel Pina to a minor league contract. |
| Jan 15 | Manuel Almeida | Signed as Free Agent | Seattle Mariners signed free agent C Manuel Almeida to a minor league contract. |
| Jan 15 | Manuel Almeida | Signed as Free Agent | Seattle Mariners signed free agent C Manuel Almeida to a minor league contract. |
| Jan 15 | Wisler Infante | Signed as Free Agent | Seattle Mariners signed free agent RHP Wisler Infante to a minor league contract. |
| Jan 15 | Henry Alcantara | Signed as Free Agent | Seattle Mariners signed free agent RHP Henry Alcantara to a minor league contract. |
| Jan 15 | Kendry Martínez | Signed as Free Agent | Seattle Mariners signed free agent SS Kendry Martínez to a minor league contract. |
| Jan 15 | Yorger Bautista | Signed as Free Agent | Seattle Mariners signed free agent OF Yorger Bautista to a minor league contract. |
| Jan 15 | Christopher Quiroz | Signed as Free Agent | Seattle Mariners signed free agent RHP Christopher Quiroz to a minor league contract. |
| Jan 15 | Cesar Farias | Signed as Free Agent | Seattle Mariners signed free agent RHP Cesar Farias to a minor league contract. |
| Jan 15 | Darwin Ramos | Signed as Free Agent | Seattle Mariners signed free agent RHP Darwin Ramos to a minor league contract. |
| Jan 15 | Blake Hunt | Trade | Baltimore Orioles traded C Blake Hunt to Seattle Mariners for cash. |
| Jan 15 | Samad Taylor | Designated for Assignment | Seattle Mariners designated 2B Samad Taylor for assignment. |
| Jan 14 | Jack López | Signed as Free Agent | Seattle Mariners signed free agent 2B Jack López to a minor league contract. |
| Jan 14 | Nick Raposo | Designated for Assignment | Seattle Mariners designated C Nick Raposo for assignment. |
| Jan 14 | Miles Mastrobuoni | Trade | Chicago Cubs traded SS Miles Mastrobuoni to Seattle Mariners for cash. |
| Jan 13 | Austin Kitchen | Designated for Assignment | Seattle Mariners designated LHP Austin Kitchen for assignment. |
| Jan 13 | Donovan Solano | Signed as Free Agent | Seattle Mariners signed free agent 3B Donovan Solano. |
| Jan 10 | Freuddy Batista | Signed as Free Agent | Seattle Mariners signed free agent C Freuddy Batista to a minor league contract. |
| Jan 9 | Yoyner Fajardo | Signed as Free Agent | Seattle Mariners signed free agent OF Yoyner Fajardo to a minor league contract. |
| Jan 9 | Tyler Jay | Claimed Off Waivers | Seattle Mariners claimed LHP Tyler Jay off waivers from Milwaukee Brewers. |
| Jan 8 | Hagen Danner | Claimed Off Waivers | Seattle Mariners claimed RHP Hagen Danner off waivers from Toronto Blue Jays. |
| Jan 3 | Josh Fleming | Status Change | LHP Josh Fleming roster status changed by Seattle Mariners. |
| Jan 3 | Josh Fleming | Signed as Free Agent | Seattle Mariners signed free agent LHP Josh Fleming to a minor league contract. |
| Jan 2 | Dylan File | Signed as Free Agent | Seattle Mariners signed free agent RHP Dylan File to a minor league contract. |