Tony Parker contributed 14 points with nine assists and Kawhi Leonard added 13 points and eight rebounds for the Spurs, who won a second road game in two nights and a fifth straight overall.
They were playing without starting center Duncan, who was given the night off.
Marco Belinelli and Patty Mills came off the bench to put in a combined 22 points for San Antonio.
The 76ers were led by with Evan Turner with 20 points.
Spencer Hawes supplied 17 points and 13 rebounds.