The loss symbolized a disappointing season for the Angels, who signed key free agents Albert Pujols and C.J. Wilson prior to the season. Los Angeles got off to a slow start and could never catch up, finishing in third place in the AL West at 89-73.
Seattle won its final two games and wound up last in the division for the third straight year.
Wells highlighted a six-run seventh inning with his home run. He also had a two-run single in the sixth that gave Seattle a 6-0 lead.
Blake Beavan (11-11) went eight innings to get the decision, surrendering seven hits.
Jered Weaver (20-5) got the start for the Angels, but went only one inning and gave up two runs to take the loss. He had a four-game winning streak snapped and concluded the year with a 2.81 earned run average.