Trout went 4 for 5 with four runs scored and three RBIs in the 10-9 win at Angel Stadium in Anaheim, Calif. His second longball gave the Angels their final advantage in the bottom of the eighth frame.
Athletics third baseman Matt Chapman went 3 for 5 with two home runs, a triple, six RBIs and three runs scored in the loss.
The Angels scored their first run on a wild pitch before Anthony Rendon clubbed a two-run shot in the bottom of the first. The Athletics rallied in the top of the next inning.
Chapman led off the half inning with a solo homer and Stephen Piscotty followed with an RBI single before the Athletics tied the game at 3-3 on a wild pitch.
Chapman hit his second home run of the game in the top of the next inning to give the Athletics a 5-3 lead.
Angels outfielder Justin Upton made the score 5-4 with an RBI single in the bottom of the third inning, but Chapman returned to do more damage at the plate in the top of the fourth frame. The Athletics third baseman swatted a three-run triple to give Oakland an 8-4 advantage. Chapman later scored on a fielding error to push the Athletics' lead to five runs.
David Fletcher struck out to lead off the bottom of the inning for the Angels. Tommy La Stella then doubled before Trout stepped up to the plate.
Athletics relief pitcher J.B. Wendelken missed the strike zone with a ball before he lobbed in a sinker for his second pitch of the exchange. Trout thumped the pitch to left field for a 428-foot home run. Albert Pujols grounded out and plated Anthony Rendon in the same inning to cut the Athletics' lead to two runs.
Angels star Shohei Ohtani smashed a two-run homer in the bottom of the sixth inning before Trout returned to the plate in the bottom of the eighth for the decisive swat.
The reigning American League MVP fell behind 1-2 in the count before Athletics relief pitcher Yusmeiro Petit threw in a 75.7-mph curveball. Trout ripped the off-speed offering over the left field fence for a go-ahead 426-foot blast.
Angels starter Julio Teheran allowed five hits and five runs in two innings in the win. Athletics starter Sean Manaea allowed seven hits and four runs in 2 2/3 innings.
Trout now has six home runs and 10 RBIs in seven games since he returned from the paternity leave list last week. He is hitting .333 with seven home runs and 14 RBIs this season
The Angels (6-11) again host the Athletics (12-5) at 9:40 p.m. EDT Tuesday at Angel Stadium.