Seattle also signed infielders Francisco Martinez, Justin Smoak and Seager, who hit 20 home runs and drove in 86 runs last season, both career bests.
Outfielders Julio Morban, Carlos Peguero, Eric Thames and Casper Wells also agreed to contracts for 2013.
The Mariners have now agreed to deals with 24 players on their 40-man roster. All players on the 40-man roster need to be signed or renewed by March 11.
Mariners pitchers and catchers will report to Peoria, Ariz., for the start of Spring Training on Feb. 12.
Corey Brock is a reporter for MLB.com. Keep track of @FollowThePadres on Twitter. This story was not subject to the approval of Major League Baseball or its clubs.