Yadier Molina, Carlos Beltran and Matt Holliday also connected for the Cardinals, who are in Milwaukee for a three-game series after opening with a victory over the Marlins in Miami on Wednesday night.
Gallardo (0-1) struggled with his control from the start and lasted only 3 2-3 innings, giving up seven hits and six runs with five walks and three strikeouts. Manager Ron Roenicke gave Gallardo the opening-day start ahead of Zack Greinke, despite Gallardo's career 1-7 record against the Cardinals with a 5.66 ERA coming into Friday's game.
Jaime Garcia (1-0) pitched six solid innings for St. Louis, yielding two runs and five hits.
Brewers fans gave a rousing reception to Braun, both before the game and the first few times he stepped to the plate. It was a show of support for the NL MVP, whose potential 50-game suspension for a positive drug test was overturned by an arbitrator before spring training.
Braun said before the game he hoped to show fans he can handle the offseason controversy and return to his MVP form after struggling in spring training.
With the Cardinals trailing 2-0 after the first inning, Molina smashed a pitch into the right-field bullpen to start the second.
Things got even worse from there.
Gallardo gave up back-to-back shots to Beltran and Holliday to start the third. Gallardo then walked Lance Berkman and gave up his third homer of the inning to Freese.
After walking Molina, Gallardo finally got three straight outs.
Roenicke lifted Gallardo after he allowed an RBI single to Freese that put the Cardinals up 6-2. Marco Estrada got the final out of the inning.
Milwaukee had runners on first and third with one out in the fifth, but Jonathan Lucroy was called for interference when he ran into Cardinals second baseman Daniel Descalso while Descalso was trying to field a grounder. Carlos Gomez flied out to end the inning.
Things started out well for the Brewers, who grabbed a 2-0 lead in the first. But they didn't score again until pinch hitter George Kottaras connected for a three-run homer in the ninth.
NOTES: Brewers principal owner Mark Attanasio said before the game that the team continues work on contract extensions for general manager Doug Melvin and Roenicke. ... Milwaukee's Norichika Aoki made his major league debut as a pinch hitter in the fifth, striking out. ... The Cardinals placed RHP Scott Linebrink on the 15-day disabled list with right shoulder capsulitis and promoted RHP Victor Marte from Triple-A Memphis.
Link to Boxscore: St. Louis 11 at Milwaukee 5