Spencer Hawes added 19 points and 12 rebounds for the 76ers, who made 16 of 22 shots to lead 40-26 after the first quarter. Thaddeus Young had 14 points and 12 rebounds.
Josh Smith, who led Atlanta with 19 points, scored to cut Philadelphia's lead to 54-45 late in the first half. A basket by Hawes pushed the lead back to double figures for good.
Al Horford had 18 points and 10 rebounds for Atlanta, which lost its second straight home game. Ivan Johnson had 17 points.
Damien Wilkins had 16 points for the 76ers, who have won four of five. Philadelphia's previous high mark for points in a period was 36 in the second quarter against Sacramento on March 26.
The 76ers are barely alive in the playoff race, sitting five games behind eighth-place Milwaukee in the Eastern Conference playoff race.
"I really like the spirit of our team coming down the stretch," said 76ers coach Doug Collins before the game. "We're not looking to be in the lotto bowl."
The Hawks began the night tied with Chicago for fifth place in the East.
Atlanta's last lead was 11-10. The 76ers pulled away by making their first five 3-pointers and made 9 of 16 overall.
Jrue Holiday, who shot just 2 of 24 from the field in Philadelphia's 88-83 loss at Charlotte Wednesday night, had more shooting struggles while making only 3 of 14 shots for nine points.
The 76ers' 40 first-quarter points matched the high mark allowed by Atlanta in any quarter this season.