The loss left the Angels two games behind Oakland in the AL wild-card chase. The A's fell to Texas 9-7 earlier Thursday.
Jesus Montero drove in two runs for Seattle, which broke the game open with a four-run seventh and avoided a three-game sweep.
Hisashi Iwakuma (8-5) got the win, allowing two runs on seven hits over six innings.
Angels' starter Dan Haren (12-12) took the loss, yielding three runs on six hits in 5 1/3 innings.
Los Angeles lost for the first time in its last six games.