Jake Buchanan (1-0) pitched five shutout innings as Chicago improved to 14-3 against Cincinnati this season with two games to play. The right-hander allowed two hits in his first start since 2014 with Houston.
Anthony Rizzo also drove in two runs for the NL Central champions, who were coming off a rare tie in Pittsburgh due to rain.
Joey Votto hit a two-run homer in the ninth for last-place Cincinnati, which announced before the game that manager Bryan Price would return next season.