Garko fills a need for the Rangers, who had been looking for a right-handed hitter to come off the bench. Chris Davis is their starting first baseman.
Texas optioned catcher Max Ramirez to Triple-A Oklahoma.
Garko is a .279 career hitter over five major league seasons with Cleveland (2005-09) and San Francisco (2009). He went to spring training with Seattle after signing a $550,000 contract, and hit .220 with a home run and four RBIs in 15 games.