McCann drove in a third run with a sacrifice fly in the fifth and Juan Francisco tacked on a solo homer in the eighth in helping the Braves earn a split of the four-game series.
Staked to an early 4-0 lead, Atlanta starter Mike Minor (5-6) lasted 6 1/3 innings to get the win. He gave up three runs, one of them unearned, on three hits with six strikeouts.
Geovany Soto hit a solo shot for the Cubs in the fifth and Reed Johnson had a two-run single in the seventh that briefly cut the Chicago deficit to three.
Matt Garza (4-7) surrendered five runs on five hits in four innings to take the loss.