Antawn Jamison paced the undermanned Cavaliers with 20 points, while Ramon Sessions and Alonzo Gee had 19 and 17, respectively, in the Cleveland's second straight loss and its sixth in the last nine games.
Cleveland was playing its third straight game without its No. 1 pick Kyrie Irving because of a concussion. The Cavs were also without guard Anthony Parker (lower back spasms) and center Anderson Varejao (broken right wrist).
Cleveland recorded the first points of the game with an Omri Casspi runner before Philadelphia reeled off a 12-3 run.
The Cavaliers, though, responded with a 12-4 swing to take a one-point lead, 17-16, with less than three minutes left in the opening frame.
Sessions sank a jumper after a Vucevic layup to put Cleveland back on top, but that would be the last time the Cavaliers would have the lead.
Philadelphia recorded the final three points of the first and held a 21-19 advantage after one. The Sixers then opened the second quarter with nine straight points, part of an 18-4 spurt, to jump out to a 39-23 cushion.
Williams tallied seven straight Philly points in the run, while Gee scored all four of the Cavaliers' points.
The Sixers held a double digit lead for the remainder of the half, leading by as much as 21 points en route to a 58-41 halftime advantage.
Cleveland never got closer than 13 in the third quarter before taking a 79-60 deficit into the fourth, where they trailed by as much as 21.
Philadelphia improved to 6-4 on the road this season, while Cleveland fell to 5-7 at home...The Sixers' bench outscored the Cavaliers', 50-32...Cleveland held a 52-40 advantage on the glass and outscored Philadelphia, 44-40, in the paint.