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 starter Mat Latos threw 87 pitches over six shutout innings in his season debut, giving up two hits while striking out four. He started the season on the disabled list while recovering from elbow and knee surgeries.
Yovani Gallardo went seven innings for the Brewers, allowing one run on six hits and two walks while striking out eight. It was the second straight strong outing for Gallardo, who struck out a season-high eight and allowed four hits in seven innings of a 1-0 victory over Pittsburgh June 8.
Latos retired the first four hitters he faced before giving up a single to Aramis Ramirez. He then retired 13 hitters in a row before Gennett outlasted him in a long at-bat with two outs in the sixth inning. Gennett, who several times just got a piece of the ball to stay alive, hit the 13th pitch into left field for a double.
Braun then hit a drive to the center field wall that was caught by Hamilton, prompting Latos to thrust his fist in the air.
The Reds grabbed a 1-0 lead in the first inning on Brandon Phillips' RBI single.
The Brewers wasted no time in taking the lead after Latos left the game. Logan Ondrusek walked Jonathan Lucroy to start the seventh inning and Carlos Gomez lined a single. Both runners advanced on Ramirez's fly out and Lucroy scored on Khris Davis' groundout.
Rickie Weeks then singled to left to give the Brewers a 2-1 lead.
Hamilton tied the score in the bottom of the inning with his third home run of the season.
NOTES: To make room for Latos on the roster, the Reds put LHP Sean Marshall on the 15-day disabled list with a strained right shoulder. ... The Brewers signed the team's top three draft picks from the draft: LHP Kodi Medeiros, SS Jacob Gatewood and OF Monte Harrison. All three were at Miller Park Saturday and took batting practice before the game. ... The Brewers will start RHP Marco Estrada (5-3) in Sunday's series finale against the Reds' Mike Leake (3-6).