Placido Polanco scored twice for the Tigers, who have won two games in a row after a five-game losing streak.
Winning pitcher Sean Douglass (4-1) gave up only three hits and one run over eight innings with two walks and four strikeouts. Fernando Rodney registered his second save.
Mariners loser Felix Hernandez (0-1) dropped his major league debut. In five innings, he yielded only two runs and three hits with two walks and four strikeouts.
Raul Ibanez drove in Seattle's lone run with his 15th homer. Seattle has lost 11 of 16 games overall.