Mariners Roster & Staff
Transactions
| Date | Transaction |
| 09/15/25 | Baltimore Orioles claimed LHP José Castillo off waivers from Seattle Mariners. |
| 09/12/25 | Seattle Mariners designated LHP José Castillo for assignment. |
| 09/12/25 | Seattle Mariners recalled RHP Casey Legumina from Tacoma Rainiers. |
| 09/06/25 | Seattle Mariners sent RHP Gregory Santos on a rehab assignment to Tacoma Rainiers. |
| 09/06/25 | Seattle Mariners activated RF Victor Robles. |
| 09/06/25 | Seattle Mariners sent RHP Gregory Santos on a rehab assignment to Tacoma Rainiers. |
| 09/05/25 | Seattle Mariners sent LHP Joe Jacques outright to Tacoma Rainiers. |
| 09/04/25 | Seattle Mariners activated LHP José Castillo. |
| 09/04/25 | Seattle Mariners optioned LHP Tayler Saucedo to Tacoma Rainiers. |
| 09/03/25 | Seattle Mariners designated LHP Joe Jacques for assignment. |
| 09/03/25 | Washington Nationals claimed RHP Sauryn Lao off waivers from Seattle Mariners. |
| 09/03/25 | Seattle Mariners claimed LHP José Castillo off waivers from New York Mets. |
| 09/02/25 | Seattle Mariners signed free agent RHP Nick Anderson to a minor league contract. |
| 09/02/25 | Seattle Mariners signed free agent RHP Guillo Zuñiga to a minor league contract. |
| 09/01/25 | Seattle Mariners released 1B Donovan Solano. |
| 09/01/25 | Seattle Mariners designated RHP Sauryn Lao for assignment. |
| 09/01/25 | Seattle Mariners recalled 2B Leo Rivas from Tacoma Rainiers. |
| 09/01/25 | Seattle Mariners selected the contract of C Harry Ford from Tacoma Rainiers. |
| 09/01/25 | Seattle Mariners selected the contract of RHP Luke Jackson from Tacoma Rainiers. |