The Sixers were strong from the opening tip, they made their first 11 shots and raced to a stunning 26-4 lead. The Heat, though, erased the deficit in the third quarter and appeared to take control behind LeBron James.
Hawes hit a 3-pointer, then a driving layup for a 109-108 lead with 2:01 left.
James blew two straight chances to put Miami up, losing the ball on a drive down the middle, then missed a 6-footer on the next possession.
Shane Battier missed his seventh straight 3-point attempt, and the Sixers put the game away from the free-throw line.
Michael Carter-Williams had 22 points, 12 assists and set an NBA first-game record with nine steals for the Sixers. Evan Turner scored 26.
LeBron James had 25 points and 13 assists and Chris Bosh scored 22 for Miami. The Heat received their NBA championship rings on Tuesday night.
Miami guard Dwyane Wade sat out to rest his sore knees. Coach Erik Spoelstra says he wanted to give Wade an extra day to recover with the Heat playing in consecutive nights. Wade scored 13 points for the Heat in their 107-95 win over Chicago on Tuesday.
For most of the game, the Sixers played more like the team in the hunt for the championship, not rebuilding. Allen Iverson, Charles Barkley, Julius Erving and Moses Malone were among the former Sixers on hand for opening night.
The Heat surely could have used Wade. Wade, though, had walked into locker room both knees wrapped in ice and an understanding it was too early in the season to push himself. He said it was "just being smart."
"It was not pre-planned, it was something our trainers and coaches came to me with," Wade said. "It's early in the season, it's just a precaution."
James said Wade could take all the time he needed.
"If he needs to take the second game of the season, the 30th game, 50th game, 80th game, that's the way it is," James said.
After all, the Heat were a double-digit favorite to rout the Sixers, and expected to have little trouble against one of the worst teams in the NBA.
Not so fast.
The Sixers dominated only hours after Iverson announced his retirement, ending a 14-year career.
Carter-Williams had a steal and dunk to open the game, Turner dunked over James, and Hawes tossed in a layup for a stunning 19-0 run to open the game. James finally banked in a shot with 7:07 left in the first to end Miami's scoring drought.
The Sixers still led 29-11 even with a lineup that included Tony Wroten, Lavoy Allen and Daniel Orton on the court.
The Heat, though, became the Heat and used a 14-0 run in the second quarter to pull to 51-49 at halftime.
James hit a 3 that made it a one-point game, and Udonis Haslem's inside layup gave the Heat their first lead of the game, 60-59. Ray Allen hit all four 3-pointers in the quarter, James made three and the Heat shot a sizzling 10 of 13 from 3-point range in the third. They finished 16 of 22 (73 percent) from the floor overall and stretched the lead to 94-85. The Heat would miss 10 straight field goals in the fourth.
But MCW turned into a fourth-quarter MVP for the Sixers. He disrupted James in the lane and was near flawless from the free-throw line.
Notes: The Heat didn't land in Philadelphia until after 3 a.m. ... Brown was an assistant for the Spurs last year. He said it was still painful to remember the way San Antonio collapsed against the Heat in the NBA finals. ... Patti LaBelle and rapper Meek Mill were at the game. Eagles wide receiver DeSean Jackson and Villanova coach Jay Wright also attended the game. ... Other former Sixers on hand included 1983 championship coach Billy Cunningham, Bobby Jones and World B. Free. ... The Sixers will retire Iverson's No. 3 on March 1.