Latos (6-2) rebounded from a poor outing in his previous start, when he was bombed for seven runs over four innings last week against the Cleveland Indians.
This time out, he tossed his second career complete game, holding Milwaukee to one run on four hits while issuing a pair of walks as the National League Central-leading Reds took the opener of a three-game series.
Jay Bruce and Brandon Phillips each supplied a run-scoring double for Cincinnati, which won for only the second time in seven games overall.
Milwaukee's Yovani Gallardo (6-6) absorbed the loss, yielding a pair of runs on four hits over six frames. The right-hander issued four walks in the defeat.
Norichika Aoki socked a solo homer for the Brewers.