"We shot ourselves in the foot tonight," Sixers center Spencer Hawes said. "I don't know how many layups, free throws, a combination of the two we missed.
"But if you can't make those, you don't deserve to win."
The Sixers (5-7) missed 10 layups and shot 38.4 percent from the field. Five of their missed layups came in the fourth quarter. The Sixers made just 12 of 22 foul shots for the game.
Those statistics overshadowed what was by far their best defensive game of the season.
"I think we played our heart out," said swingman Evan Turner, whose team suffered a 37-point setback at New Orleans on Saturday. "Once again, we didn't help ourselves out at the free-throw line. But we just have to keep up the intensity."
The Sixers pulled within 90-87 on James Anderson's three-pointer with 3 minutes, 23 seconds remaining.
But Jose Calderon drained a three-pointer. Then Dirk Nowitzki made a technical foul shot after Turner was whistled for arguing a no-call. Shawn Marion dunked to give the Mavs a 96-87 cushion with 2:13 left.
Monta Ellis led Dallas with 24 points and 10 assists. Nowitzki had 20 points and 10 rebounds, while Marion added 20 points and seven boards.
Turner finished with 26 points to lead the Sixers.
Point guard Tony Wroten finished 19 points and five steals while starting in place of Michael Carter-Williams (bruised left foot) for the fourth straight game. Power forward Thaddeus Young added 12 points and 11 rebounds but shot just 6 for 18 from the field.
Early on, the game was flat-out ugly.
The teams combined to miss their first 12 shots until Turner hit an 18-foot jumper 2:38 into the first quarter. The Sixers took a 21-18 lead into the second.
The Mavs ended the half with a 10-4 run to pull within 47-43 at the break.
The Mavericks knotted the score at 60 on a Nowitzki jumper in the third quarter.
But the Sixers responded with a 7-0 run to take a 67-60 lead with 3:45 left in the quarter. The Mavs answered with a 6-0 run before Turner's foul shot made it a 69-66 game. Dallas went on to take its first lead (70-69) on Marion's dunk with 1:44 left in the quarter. Dallas took a 74-71 advantage into the fourth.
Point guard Shane Larkin made his NBA debut for the Mavericks four months after he broke his right ankle in practice. Larkin finished with three points, three assists and three steals.
Carter-Williams took some jumpers at Monday's shootaround. His status for Wednesday's game against the Toronto Raptors at the Wells Fargo Center has not been determined.
"The old day-to-day cliché is going to rule the day," Sixers coach Brett Brown said.