Andre Iguodala scored a season-high 28 points as Philadelphia scored their 13th home win in 15 tries against Miami. The loss dropped the Heat to 8-21, the worst record in the Eastern Conference and the second worst in the NBA.
Philadelphia (12-16) led by as many as 19 points in the second half but had to fight off a Miami comeback bid in the fourth quarter.
"We just didn't have it," Miami coach Pat Riley said.
"We weren't playing hard. We were obviously out of sync."
The Heat rallied from a 55-38 halftime deficit to close to within three points in the fourth quarter, but could get no closer. Miami shot just 40 percent, including a woeful 1-for-13 from three-point range.
Dwyane Wade led the Heat with 27 points but was frustrated with his team's struggles.
"It's tough to lose," Wade said. "But it's tougher to be the worst team in the Eastern Conference."
Ricky Davis had 21 points for the Heat, while Shaquille O'Neal had 10 rebounds but was held to five points.
The Orlando Magic snapped a four-game home losing streak with a 110-96 win over the New York Knicks. Hedo Turkoglu led Orlando with 26 points.
The Washington Wizards snapped a three-game losing streak with a 108-104 win over the Charlotte Bobacts.
The Detroit Pistons won their sixth in a row with a 101-83 win over the New Jersey Nets.
The Chicago Bulls lost 94-78 to the San Antonio Spurs. Tony Parker led San Antonio with 28 points.
The Utah Jazz snapped the Dallas Mavericks' five-game winning streak with a 99-90 victory, Carlos Boozer leading the way for the victors with 21 points.
Marcus Camby had an unusual triple-double -- 10 points, 11 rebounds and 10 blocks -- as the Denver Nuggets mauled the Milwaukee Bucks 125-105.
The Boston Celtics won for the first time in Sacramento in nearly 12 years, downing the Kings 89-69 to improve to 23-3 on the season.