Wilkin Castillo was 3-for-4 with an RBI and a run scored and Jay Bruce had two hits and two runs for the Reds, who have won four of their last five games.
Reds starter Edinson Volquez gave up four runs on five hits with three walks and 10 strikeouts in 5 2/3 innings.
Jared Burton (5-1) got the win for pitching a scoreless eighth inning.
Jason Kendall hit a two-run home run and J.J. Hardy added a solo homer for the Brewers.
Milwaukee starter Dave Bush allowed just two runs on seven hits in eight innings.
Salomon Torres (6-5) blew his seventh save of the season and was charged with the loss.