Logan O'Hoppe hit two home runs, doubled and had three RBIs and Brandon Drury also went deep for the Angels (68-77), who won their third consecutive game.
Cal Raleigh and Julio Rodriguez homered for the Mariners (79-65), who have lost four in a row to drop a half-game behind the Texas Rangers (79-64) in the race for the American League's third and final wild-card berth. Seattle trails the first-place Houston Astros (82-63) by 2 1/2 games in the AL West.
With Kyren Paris the runner at second to start the 11th, Eduardo Escobar grounded a one-out single to right off Trent Thornton (0-2), sending Paris to third. Grichuk then lined a single to center to put Los Angeles ahead. A two-out fielding error by third baseman Eugenio Suarez and an RBI single by Nolan Schanuel brought home the final two runs.
Jose Marte (1-0) got his first major league victory despite allowing two runs in the bottom of the 10th. Jimmy Herget pitched a 1-2-3 bottom of the 11th for his first save of the season.
Both teams left the bases loaded while failing to score in the ninth inning, then Drury and Rodriguez exchanged two-run homers in the 10th.
The Mariners scored three runs off Angels left-hander Reid Detmers in the first inning. Following singles by J.P. Crawford and Rodriguez, Teoscar Hernandez hit a towering shot to right, with Jordyn Adams making a leaping catch at the wall to turn a potential three-run homer into a sacrifice fly. Raleigh then hammered a two-run shot into the Mariners' bullpen in left-center field to make it 3-0.
The Angels answered in the top of the second against Mariners right-hander Logan Gilbert. Mike Moustakas led off with a single to right, and O'Hoppe lined the next pitch just over the wall in left to pull Los Angeles within 3-2.
O'Hoppe tied it at 3-3 with a solo shot to left with one out in the fourth on a 2-2 pitch.
Detmers settled down and went seven innings, allowing three runs on five hits with no walks and seven strikeouts.
Gilbert also went seven and gave up three runs on six hits, with one walk and five strikeouts.
Angels designated hitter Shohei Ohtani was scratched from the lineup and missed his eighth consecutive game with a strained right oblique.
—Field Level Media