With one out in the eighth inning, Scooter Gennett ended up with a double after blooping a ball to center that Billy Hamilton got his glove on but couldn't hold. Braun then drove the first pitch from reliever J.J. Hoover (1-5) over the right field fence for his 10th homer of the season.
Francisco Rodriquez pitched a scoreless ninth inning for his 21st save in 23 opportunities. Will Smith (1-0) got the win despite giving up a game-tying home run to Hamilton in the eighth inning.
Reds pitcher Mat Latos gave up just two hits in six innings in his season debut.
Brewers starter Yovani Gallardo allowed one run on six hits in seven innings and struck out eight.