TJ Friedl drove in two runs with a hit in the first inning, Tyler Stephenson also added an RBI during a three-run second inning, and Spencer Steer contributed with a double in the eighth to drive in another run.
Tony Santillan took the mound for the Reds because Frankie Montas, the scheduled starter, was traded to Milwaukee earlier in the day. The Reds used seven pitchers to limit the Cubs to three runs and seven hits.
Nick Martinez (5-5) threw four scoreless innings to earn the win, and Alexis Díaz closed out the game with his 21st save in 23 chances.
With Montas traded, Martinez might be making a case to join the starting rotation.