Vargas (2-1) allowed one run on three hits and struck out five to give the Mariners their sixth win in their last seven games.
Orioles' starter David Hernandez (0-3) gave up all three runs on seven hits in 6 1/3 innings. Nolan Reimold drove in the only run for Baltimore with a double in the first inning.
Hernandez threw a wild pitch in a two-run Seattle end of the first that put two runners in scoring position. Ichiro Suzuki then came home on Gutierrez's sacrifice fly. Bradley singled home Chone Figgins to make it 2-1 after Hernandez had walked Ken Griffey Jr. with two outs.
The Mariners added a run in the seventh on consecutive doubles by Adam Moore and Wilson.