Mariners Roster & Staff
Transactions
| Date | Transaction |
| 01/31/20 | Philadelphia Phillies claimed Reggie McClain off waivers from Seattle Mariners. |
| 01/30/20 | Seattle Mariners signed free agent RHP Yoshihisa Hirano. |
| 01/30/20 | Seattle Mariners designated LHP Ricardo Sanchez for assignment. |
| 01/29/20 | Seattle Mariners signed free agent LHP Dietrich Enns to a minor league contract. |
| 01/24/20 | Seattle Mariners designated RHP Reggie McClain for assignment. |
| 01/24/20 | Seattle Mariners claimed Nick Margevicius off waivers from San Diego Padres. |
| 01/24/20 | Seattle Mariners signed free agent 2B Alen Hanson to a minor league contract and invited him to spring training. |
| 01/24/20 | Seattle Mariners signed free agent 2B Alen Hanson to a minor league contract. |
| 01/22/20 | Seattle Mariners invited non-roster 3B Jordan Cowan to spring training. |
| 01/22/20 | Seattle Mariners invited non-roster RHP Darren McCaughan to spring training. |
| 01/22/20 | Seattle Mariners invited non-roster RHP Joey Gerber to spring training. |
| 01/22/20 | Seattle Mariners invited non-roster LHP Aaron Fletcher to spring training. |
| 01/22/20 | Seattle Mariners invited non-roster RHP Sam Delaplane to spring training. |
| 01/22/20 | Seattle Mariners invited non-roster RHP Jack Anderson to spring training. |
| 01/22/20 | Seattle Mariners invited non-roster C Cal Raleigh to spring training. |
| 01/22/20 | Seattle Mariners invited non-roster LHP Anthony Misiewicz to spring training. |
| 01/22/20 | Seattle Mariners invited non-roster RHP Wyatt Mills to spring training. |
| 01/22/20 | Seattle Mariners invited non-roster LHP Ian McKinney to spring training. |
| 01/22/20 | Seattle Mariners invited non-roster RHP Logan Gilbert to spring training. |
| 01/22/20 | Seattle Mariners invited non-roster OF Luis Liberato to spring training. |
| 01/22/20 | Seattle Mariners invited non-roster RHP Ljay Newsome to spring training. |
| 01/22/20 | Seattle Mariners invited non-roster RHP Penn Murfee to spring training. |
| 01/22/20 | Seattle Mariners invited non-roster C Joseph Odom to spring training. |
| 01/22/20 | Seattle Mariners signed free agent C Joe Hudson to a minor league contract and invited him to spring training. |
| 01/22/20 | Seattle Mariners invited non-roster 3B Connor Hoover to spring training. |
| 01/22/20 | Seattle Mariners invited non-roster OF Jarred Kelenic to spring training. |
| 01/22/20 | Seattle Mariners invited non-roster OF Julio Rodriguez to spring training. |
| 01/15/20 | Seattle Mariners signed free agent RHP Chasen Bradford to a minor league contract. |
| 01/10/20 | Seattle Mariners claimed Sam Haggerty off waivers from New York Mets. |
| 01/08/20 | Seattle Mariners signed free agent SS Ryan McLaughlin to a minor league contract. |
| 01/07/20 | Seattle Mariners selected the contract of RHP Kevin Munson from Southern Maryland Blue Crabs. |
| 01/07/20 | Seattle Mariners signed free agent C Justin Novak to a minor league contract. |