Jay Bruce had a solo homer and two RBI and Joey Votto drove in a run for the Reds, who have won two straight.
Cincinnati starter Edinson Volquez (1-1) got the victory, allowing six runs on seven hits in five innings, with four walks and four strikeouts. Jared Burton, Arthur Rhodes and David Weathers each pitched one inning of shutout relief and Francisco Cordero got a save, his second of 2009.
Yovani Gallardo (1-1) took the loss, giving up seven runs on three hits with three strikeouts and four walks over five innings.
Corey Hart belted a three-run homer and J.J. Hardy homered for Milwaukee, which has lost three straight.