Colorado had taken an 8-7 lead in the ninth inning on a two-run home run by Carlos Gonzalez, but Bryant hit the second pitch he saw from John Axford (3-4) over the wall in left-center to give Chicago a dramatic victory and snap a three-game skid.
Trailing 7-4, the Rockies scored four times in the ninth to move ahead. Jason Motte started the ninth by allowing a pinch-home run to Daniel Descalso, a single to Charlie Blackmon and a double to D.J. LeMahieu.
Rafael Soriano (1-0), added to the roster July 20, then came on and gave up Troy Tulowitzki's run-scoring grounder before Gonzalez roped a two-run home run into right to put Colorado in front.