Bumgarner (14-7) baffled the Dodgers on four hits, stranding runners on third base in the second and sixth innings en route to his third victory in four starts.
The left-hander struck out 10 and didn't issue a walk for the Giants, who vaulted over the Dodgers into the National League West lead by a half game.
Pablo Sandoval contributed a first-inning sacrifice fly and an RBI single in the sixth to account for the Giants' offense.
Clayton Kershaw (11-7) fanned 10 and didn't walk a batter, but absorbed the hard-luck loss for the Dodgers. The reigning National League Cy Young Award winner yielded a pair of runs on six hits over eight frames.