Milwaukee entered the day trailing St. Louis by 4 1/2 games for the final NL wild-card spot, a long shot that left no margin for error.
Shaun Marcum (6-4) went six innings for his first victory since returning from an elbow problem, allowing only four hits, including Joey Votto's RBI double.
Norichika Aoki homered to start a three-run third inning off Bronson Arroyo (12-9) and added an RBI double. Braun, the NL's Most Valuable Player last season as the Brewers won the NL Central, hit a two-run shot in the seventh off Logan Ondrusek.
The Reds have clinched the Central title.
