With the win, the Cubs improved to 20-6 in August, while the loss snapped the Pirates' win streak at four. Chicago is 7-4 in extra-inning games.
Josh Bell smacked a solo homer in the fourth and Gregory Polanco hit a three-run homer in the sixth to help the Pirates open a 6-3 lead. But Cubs rookie Willson Contreras belted a two-run homer in the eighth off Neftali Feliz, and Jorge Soler tied the game at 6 with a one-out blast in the ninth off Tony Watson.