Mariners Roster & Staff
Transactions
| Date | Transaction |
| 08/18/26 | Seattle Mariners signed free agent 2B Andy Ibáñez to a minor league contract. |
| 08/15/26 | Seattle Mariners optioned RHP Troy Watson to Tacoma Rainiers. |
| 08/15/26 | Seattle Mariners claimed RHP Troy Watson off waivers from Detroit Tigers. |
| 08/14/26 | Seattle Mariners placed SS Colt Emerson on the 10-day injured list. Left wrist tendon inflammation. |
| 08/14/26 | Seattle Mariners selected the contract of 2B Brock Rodden from Tacoma Rainiers. |
| 08/14/26 | Seattle Mariners optioned C Willie MacIver to Tacoma Rainiers. |
| 08/13/26 | Seattle Mariners signed free agent LHP Lael Lockhart to a minor league contract. |
| 08/12/26 | Seattle Mariners signed free agent RHP Scott Effross to a minor league contract. |
| 08/12/26 | Seattle Mariners claimed C Willie MacIver off waivers from Toronto Blue Jays. |
| 08/11/26 | Seattle Mariners activated LHP Gabe Speier. |
| 08/11/26 | Seattle Mariners signed free agent RHP Conor Larkin to a minor league contract. |
| 08/11/26 | Seattle Mariners sent RHP Carlos Vargas on a rehab assignment to Tacoma Rainiers. |
| 08/10/26 | Seattle Mariners claimed RHP Nolan Kingham off waivers from Texas Rangers. |
| 08/08/26 | Seattle Mariners sent RHP Carlos Vargas on a rehab assignment to Everett AquaSox. |
| 08/08/26 | Seattle Mariners sent RHP Carlos Vargas on a rehab assignment to Everett AquaSox. |
| 08/08/26 | Seattle Mariners signed free agent CF Stuart Fairchild to a minor league contract. |
| 08/08/26 | LHP Gabe Speier roster status changed by Seattle Mariners. |
| 08/07/26 | Seattle Mariners placed RHP Cole Wilcox on the 15-day injured list. Left oblique strain. |
| 08/07/26 | Seattle Mariners recalled RHP Nick Davila from Tacoma Rainiers. |
| 08/07/26 | Seattle Mariners sent CF Stuart Fairchild outright to Tacoma Rainiers. |
| 08/05/26 | Seattle Mariners signed free agent RHP Seth Shuman to a minor league contract. |
| 08/04/26 | Seattle Mariners released DH Rob Refsnyder. |
| 08/04/26 | Seattle Mariners released C Mitch Garver. |
| 08/04/26 | Seattle Mariners activated RHP Seranthony Domínguez. |
| 08/04/26 | Seattle Mariners activated LF Taylor Ward. |
| 08/04/26 | Seattle Mariners activated 3B Brendan Donovan from the 10-day injured list. |
| 08/04/26 | Seattle Mariners designated CF Stuart Fairchild for assignment. |
| 08/04/26 | Seattle Mariners recalled C Jhonny Pereda from Tacoma Rainiers. |
| 08/03/26 | LF Taylor Ward roster status changed by Seattle Mariners. |
| 08/03/26 | Baltimore Orioles traded LF Taylor Ward to Seattle Mariners for RHP Alex Hoppe, RHP Brock Moore and RHP Harrison Kreiling. |
| 08/03/26 | Baltimore Orioles traded LF Taylor Ward to Seattle Mariners for RHP Alex Hoppe, RHP Brock Moore and RHP Harrison Kreiling. |
| 08/03/26 | Baltimore Orioles traded LF Taylor Ward to Seattle Mariners for RHP Alex Hoppe, RHP Brock Moore and RHP Harrison Kreiling. |
| 08/03/26 | Baltimore Orioles traded LF Taylor Ward to Seattle Mariners for RHP Alex Hoppe, RHP Brock Moore and RHP Harrison Kreiling. |
| 08/02/26 | San Francisco Giants claimed 1B Buddy Kennedy off waivers from Seattle Mariners. |
| 08/02/26 | Seattle Mariners traded RHP Luis Castillo to Chicago White Sox for RHP Seranthony Domínguez, C Boston Smith, RF Nolan Jones and cash. |
| 08/02/26 | Seattle Mariners traded RHP Luis Castillo to Chicago White Sox for RHP Seranthony Domínguez, C Boston Smith, RF Nolan Jones and cash. |
| 08/02/26 | Seattle Mariners traded RHP Luis Castillo to Chicago White Sox for RHP Seranthony Domínguez, C Boston Smith, RF Nolan Jones and cash. |
| 08/02/26 | Seattle Mariners traded RHP Luis Castillo to Chicago White Sox for RHP Seranthony Domínguez, C Boston Smith, RF Nolan Jones and cash. |
| 08/02/26 | Seattle Mariners recalled LHP Josh Simpson from Tacoma Rainiers. |
| 08/01/26 | Seattle Mariners placed RF Luke Raley on the 10-day injured list retroactive to July 31, 2026. Left forearm strain. |
| 08/01/26 | Seattle Mariners selected the contract of CF Stuart Fairchild from Tacoma Rainiers. |