Dirk Nowitzki and Shawn Marion had 20 points apiece for the Mavericks, who began a stretch of seven out of nine games in Dallas. Nowitzki had 10 rebounds, and Marion chipped in seven.
Ellis had 19 points in the second half and added a game-high 10 assists and two of Dallas' 11 blocked shots.
Two nights after a 35-point loss in New Orleans, the Sixers held the Mavericks scoreless for the first 5 minutes and led by 10 in the first half.
Even after losing its lead for good late in the third quarter, Philadelphia stayed close behind Evan Turner, Tony Wroten and some late 3-pointers from James Anderson.
Turner had 26 points, nine rebounds and seven assists while Wroten had 19 points and five steals.
The Mavericks pulled even twice in the third quarter before finally taking their first lead when Vince Carter knocked the ball loose as Hollis Thompson was going up for a layup.
Jae Crowder ended up with the ball on a breakaway but gave it up to Marion for the dunk and a 70-69 Dallas lead with 1:44 remaining.
Philadelphia had the ball down just 90-87 in the fourth, but Samuel Dalembert had one of his three blocks on a drive by Turner.
Jose Calderon was wide open for a short jumper on the other end but passed before getting the ball back beyond the arc and hitting for a 93-87 lead. Calderon had 14 points and was 4 of 10 from long range.
Anderson finished with 14, including 3-of-7 shooting from 3-point range. Thaddeus Young struggled from the field at 6 of 18 but still finished with a double-double at 12 points and 11 rebounds. Spencer Hawes had 10 points and 11 boards.
The Sixers held the Mavericks to a season-low 43 points in the first half. Wroten frequently found his way into the lane and matched Turner with 12 points before halftime.
Wroten and Turner combined to make 10 of 17 from the field before halftime while their teammates were just 10 of 34. Philadelphia shot 39 percent as a team in the first half.
Ellis, who has the most games of at least 18 points to start a Dallas career at 11, didn't get his first basket until the 2:12 mark of the second quarter. But it wasn't because he was missing. He was just 2 of 4 from the field before halftime.
Mavericks coach Rick Carlisle changed his lineup for the first time this season, inserting forward Jae Crowder for Dalembert, who was the starting center for the first 10 games. But the move backfired.
Crowder went 0 for 5 with two turnovers while Dallas went scoreless before Nowitzki hit a baseline jumper exactly 5 minutes in after Marion rebounded a missed 3-pointer by Crowder.
NOTES: Dallas rookie PG Shane Larkin made his NBA debut late in the first quarter, four months after breaking his right ankle in the final practice before summer league. He immediately had a steal, and his first assist was on a bucket by Nowitzki. He finished three points, three assists and three steals. ... The teams combined for 12 missed shots to start the game before Turner hit a jump shot with 9:10 left in the first quarter.