Mariners Roster & Staff
Transactions
| Date | Transaction |
| 05/31/25 | 1B Dalton Davis assigned to Seattle Mariners. |
| 05/31/25 | Seattle Mariners activated RHP Bryce Miller from the 15-day injured list. |
| 05/31/25 | Seattle Mariners designated RHP Will Klein for assignment. |
| 05/31/25 | Seattle Mariners optioned RHP Casey Legumina to Tacoma Rainiers. |
| 05/31/25 | Seattle Mariners selected the contract of SS Cole Young from Tacoma Rainiers. |
| 05/31/25 | Seattle Mariners optioned 2B Leo Rivas to Tacoma Rainiers. |
| 05/30/25 | Seattle Mariners sent RHP Trent Thornton on a rehab assignment to Tacoma Rainiers. |
| 05/30/25 | Seattle Mariners sent RHP Trent Thornton on a rehab assignment to Tacoma Rainiers. |
| 05/29/25 | Seattle Mariners designated C Blake Hunt for assignment. |
| 05/29/25 | Seattle Mariners sent RHP Logan Gilbert on a rehab assignment to Tacoma Rainiers. |
| 05/29/25 | Seattle Mariners sent RHP Logan Gilbert on a rehab assignment to Tacoma Rainiers. |
| 05/29/25 | Seattle Mariners optioned RHP Blas Castaño to Tacoma Rainiers. |
| 05/29/25 | Seattle Mariners selected the contract of RHP Casey Lawrence from ACL Mariners. |
| 05/28/25 | Seattle Mariners activated RHP Jackson Kowar from the 60-day injured list. |
| 05/28/25 | Seattle Mariners optioned RHP Logan Evans to Tacoma Rainiers. |
| 05/26/25 | Seattle Mariners sent RHP Jesse Hahn outright to Tacoma Rainiers. |
| 05/26/25 | Seattle Mariners sent 1B Austin Shenton outright to Tacoma Rainiers. |
| 05/24/25 | Seattle Mariners signed free agent RHP Casey Lawrence to a minor league contract. |
| 05/23/25 | Seattle Mariners designated RHP Jesse Hahn for assignment. |
| 05/23/25 | Seattle Mariners recalled RHP Blas Castano from Tacoma Rainiers. |
| 05/23/25 | Seattle Mariners sent RHP Casey Lawrence outright to Tacoma Rainiers. |
| 05/22/25 | Seattle Mariners activated RHP George Kirby from the 15-day injured list. |
| 05/22/25 | Seattle Mariners optioned RHP Troy Taylor to Tacoma Rainiers. |
| 05/21/25 | Seattle Mariners activated RHP Jesse Hahn. |
| 05/21/25 | Seattle Mariners designated RHP Casey Lawrence for assignment. |
| 05/21/25 | Seattle Mariners selected the contract of RHP Jesse Hahn from Tacoma Rainiers. |
| 05/20/25 | Seattle Mariners designated 1B Austin Shenton for assignment. |
| 05/20/25 | Seattle Mariners optioned LHP Jhonathan Díaz to Tacoma Rainiers. |
| 05/20/25 | Seattle Mariners selected the contract of RHP Casey Lawrence from Tacoma Rainiers. |
| 05/14/25 | Seattle Mariners placed RHP Bryce Miller on the 15-day injured list retroactive to May 12, 2025. Right elbow inflammation. |
| 05/14/25 | Seattle Mariners recalled LHP Jhonathan Díaz from Tacoma Rainiers. |
| 05/13/25 | Seattle Mariners signed free agent OF Tomo Otosaka to a minor league contract. |
| 05/10/25 | Seattle Mariners sent RHP Jackson Kowar on a rehab assignment to Tacoma Rainiers. |
| 05/09/25 | Seattle Mariners placed RHP Trent Thornton on the 15-day injured list retroactive to May 6, 2025. Appendicitis. |
| 05/09/25 | Seattle Mariners recalled RHP Troy Taylor from Tacoma Rainiers. |
| 05/08/25 | Seattle Mariners traded RHP Luis F. Castillo to Baltimore Orioles for cash. |
| 05/07/25 | Seattle Mariners activated CF Leody Taveras. |
| 05/07/25 | Seattle Mariners signed free agent RHP Casey Lawrence to a minor league contract. |
| 05/07/25 | Seattle Mariners optioned LF Rhylan Thomas to Tacoma Rainiers. |
| 05/06/25 | Seattle Mariners designated RHP Luis F. Castillo for assignment. |
| 05/06/25 | Seattle Mariners activated 3B Dylan Moore from the 10-day injured list. |
| 05/06/25 | Seattle Mariners designated RHP Luis F. Castillo for assignment. |
| 05/06/25 | Seattle Mariners claimed CF Leody Taveras off waivers from Texas Rangers. |
| 05/06/25 | Seattle Mariners optioned 2B Samad Taylor to Tacoma Rainiers. |
| 05/04/25 | Seattle Mariners sent RHP George Kirby on a rehab assignment to Tacoma Rainiers. |
| 05/03/25 | Seattle Mariners activated RHP Matt Brash from the 15-day injured list. |
| 05/03/25 | Seattle Mariners sent RHP Jackson Kowar on a rehab assignment to ACL Mariners. |
| 05/03/25 | Seattle Mariners sent RHP Jackson Kowar on a rehab assignment to ACL Mariners. |
| 05/03/25 | Seattle Mariners optioned RHP Troy Taylor to Tacoma Rainiers. |
| 05/02/25 | Seattle Mariners sent RHP Sauryn Lao outright to Tacoma Rainiers. |