After flying out twice to deep center field, Pujols hit his first home run in the eighth inning off Chad Qualls.
The Cardinals' slugger hit only three homers in May, and even Pujols was wondering where his power had gone. Patience helped him find it again.
"If you tell me I was trying to do too much, maybe, I don't know," he said. "I chased a lot of bad pitches early. Now, I just let the pitcher come to me. If I have to take my walk, I'll take my walk."
Pujols sent fly balls deep to straightaway center in his first two at-bats, drives that might've been homers in other ballparks. Rookie center fielder Hunter Pence had to trot up Tal's Hill to make both plays.
"Today, I wanted to make sure I hit the ball and put my good swing on it," Pujols said. "That's what I did. Could it have been four homers? Who knows? I'll take two and take the win."
David Eckstein and Juan Encarnacion also homered for the Cardinals, who've won four of their past five. St. Louis went 10-14 in April and 12-15 in May, but the Cardinals are sensing things are finally coming together.
The victory kept St. Louis 6½ games behind Milwaukee in the NL Central.
"I tell the guys all the time, it's there," Pujols said. "We need to go get it, play the game the right way and do the little things we need to do."
Pujols' first homer gave St. Louis a 5-4 lead.
Pence, the Astros' most dependable hitter this season, tied the game again in the bottom of the eighth with a solo homer off Ryan Franklin.
Wheeler (0-2) relieved Qualls and pitched a perfect ninth inning. He got Aaron Miles on a groundout leading off the 10th before Taguchi homered off the left-field foul pole. Eckstein singled and one out later, Pujols crushed a 3-2 pitch from Wheeler high off the brick facade in left-center for an 8-5 lead.
"What a day," St. Louis manager Tony La Russa said of Pujols. "If you've been wondering about his power, watch that game today."
Jason Isringhausen (2-0) gave up a homer to Mark Loretta leading off the 10th inning. Craig Biggio then flew out. Pence singled and was forced out at second on Carlos Lee's grounder to Miles. Isringhausen then walked Luke Scott, but pinch-hitter Jason Lane flew out to end the game.
Houston has lost 14 of its past 17 games.
After Sunday's loss, Lane was sent to Triple-A Round Rock and Chris Burke was called up to replace him.
"Obviously, I'd like to play on the big league level," Lane said, "but there aren't that many at-bats here right now."
Eckstein hit the third pitch of the game into the left-field seats for his second homer of the season. Both were leadoff homers.
Pujols said the shot inspired everyone in the Cardinals' dugout.
"Today, we came out ready to rock," Pujols said. "Eck came out and hit that home run and sent a message right away that we were ready to play."
Houston starter Jason Jennings allowed only one more hit before Encarnacion led off the fifth with a solo homer off the brick facade in left field, his second homer of the season. Ludwick and Gary Bennett followed with back-to-back doubles to put the Cardinals up 3-0.
Cardinals starter Braden Looper allowed three singles through the first five innings.
Orlando Palmiero pinch-hit for Jennings leading off the sixth and scored on Pence's two-out single to center. Pence is hitting .436 (17-for-39) with a homer and seven RBI in his past 11 games. He's also caught Pujols' eye.
"It's fun to watch him play," Pujols said. "He's having fun, he can swing the bat, he can play great defense. Guys like that make you more fired up for the game."
Lance Berkman, who didn't start for the second time this season, pinch-hit for Houston reliever Dave Borkowski and hit a grounder to Spiezio, who threw to second to force out Everett. Ensberg scored on the play to make it 4-3.
Franklin relieved Flores and Loretta blooped a single to right to score Munson and tie the game at four-all.
- Eckstein homered against the Astros for the second time in his career.
- Pence has multiple hits in nine of his past 11 starts. He has four homers and 14 RBI in his past 21 games.
- Pujols has 18 multi-homer games in his career.