Chicago escaped a jam in the bottom of the ninth to get the win after the Cubs had faced an early 3-1 deficit.
Welington Castillo brought the Cubs within one with a fourth-inning RBI double and Nate Schierholtz created a 3-3 tie with a homer in the sixth.
After the Cubs took the lead in the top of the ninth, Chicago closer Carlos Marmol walked Donovan Solano to open the bottom half of the inning and then gave up a single to Austin Kearns. A sacrifice attempt by Juan Pierre turned into a force play at third to erase Solano and Marmol then retired the next two batters to collect his second save.
The win went to Shawn Camp (1-1), who worked a perfect eighth.
Steve Cishek (1-3) gave up the homer to Valbuena.