Volquez (5-5) yielded just one run on six hits and overcame three walks after being pounded for nine runs in 2 1/3 frames in his previous outing against Colorado.
Nick Vincent struck out Justin Upton to end the game, notching his first career save after the Braves had scored a run in the ninth.
Denorfia's two-run shot in the fifth put the Padres ahead 5-1 and proved to be the decisive blow as San Diego took a third straight win from the National League East leaders.
Logan Forsyth contributed two RBI in the victory.
Braves starter Paul Maholm (7-5) was reached for five runs (four earned) on seven hits over 5 2/3 innings.
Upton went 2-for-5 with a solo homer and two RBI in the loss.