Dominguez's hit was nice, but the Astros were far more excited about a single that started that inning.
That hit was by Cody Clark and it was the first of his major-league career in his 11th big league game.
"I think that was one of the happiest moments of the season," manager Bo Porter said. "Some people may think it's one hit, but ... you appreciate just the story line of the whole thing. Eleven years in the minors, getting an opportunity to come to the big leagues and being able to live out your dreams. It couldn't happen to a better guy."
First base coach Dave Clark (no relation) greeted Cody Clark with a hug as the player smiled sheepishly. Many of the Astros stood and cheered on the railing of the dugout while Jose Altuve jumped in the air and pumped his fist to celebrate the milestone.
"It was amazing," Cody Clark said. "I can't even describe it because they've been so supportive of me. Every day they're telling me 'You're going to get it. Don't worry; you're going to get it.' It was good to score a run and get in there and give them all high-fives and hugs."
Altuve hit a three-run homer in the third as the Astros got their fourth straight win.
The Astros trailed by 1 entering the fifth before Trevor Crowe singled in two runs to put Houston up 5-4. Dominguez then hit his 20th homer off the wall in left field to extend the lead to 9-4.
Dallas Keuchel (6-9) yielded 10 hits and six runs, but tied his career high by striking out nine in 5 2/3 innings for his first win since July 27. Josh Fields struck out two in a scoreless ninth for his fifth save.
Houston tagged Angels starter Jason Vargas (8-7) for nine hits and a season-high eight runs in 4 1/3 innings.
"This is one of the most unusual nights we've had in the last three weeks," Los Angeles manager Mike Scioscia said. "We just didn't get it done on the mound."
Mark Trumbo hit a two-run triple in the third and Chris Iannetta hit a solo homer in the fourth for Los Angeles, which dropped to 10-7 against Houston this season.
A pair of walks and a single by Erick Aybar loaded the bases for the Angels with no outs in the eighth inning. Trout's bases-loaded walk got Los Angeles within 9-7, but Trumbo grounded into a double play to limit the damage.
In his first game back from the disabled list, Howie Kendrick singled with two outs in the third before Trout drew a walk. Trumbo's triple, which rolled up Tal's Hill in center field, scored both of them to make it 2-0.
Astros' right fielder L.J. Hoes singled in the third before a one-out single by Brandon Barnes. Altuve launched his fifth homer into the Crawford Boxes in left field to give Houston a 3-2 lead.
Iannetta sent the first pitch of the fourth inning into the seats in left field to tie it at 3-all. Andrew Romine's RBI single with one out put Los Angeles up 4-3.
Crowe had three hits to end a 0-for-12 skid and Dominguez pushed his RBI total to 74.
Romine added an RBI single in the sixth and Aybar doubled in another run home to cut the lead to 9-6.
Los Angeles right-hander Jered Weaver opposes Brett Oberholtzer when the series continues on Saturday. ... Kendrick, who had a hyperextended left knee, was back in the lineup for the first time since Aug. 5. He was activated from the disabled list on Tuesday. He was injured when he landed awkwardly trying to avoid a collision with a teammate. Scioscia said they'll try to "get him acclimated to playing" and slowly increase his work. He was replaced in the bottom of the eighth inning. ... Houston C Jason Castro (right knee) sat out Friday, and hopes to be the designated hitter sometime in this weekend series. Manager Bo Porter said he doesn't know when Castro will catch again. ... The Astros activated OF J.D. Martinez, who had been on the disabled list since July 27 with a sprained left wrist, before Friday's game.