Sidekick Dwyane Wade contributed 22 points to spark the Heat's eighth consecutive win.
The Cavs (4-11) have now lost four in a row, as well as seven of their last eight overall.
James, who left the Cavs via free agency in 2010, added eight rebounds and eight assists. He converted on 9-of-19 shots from the field, 1-of-3 from the 3-point line and 9-of-11 from the foul line. He's now 10-1 vs. the Cavaliers since he left town.
Forward Earl Clark, the Cavs' most accurate 3-point shooter, added 13 points. He made 3-of-5 shots from behind the arc.
That prosperity ended quickly. James drained a 3-pointer and later a free throw for a 15-point bulge, 68-53, their largest lead of the game.
Things unraveled quickly in the second quarter for CLEVELAND. The Cavs made just 5-of-25 shots (20 percent) in the period and the Heat outscored them 27-14 in the second to take a 49-42 lead at halftime.
Miami shot 52.9 percent from the field in the first half, while the Cavs plummeted to 35.6 percent.
The Cavs shot a sizzling 55 percent from the floor in the first quarter and outrebounded the Heat, 13-4.
NOTES: ESPN's Chris Broussard reported that the Cavaliers are shopping G Dion Waiters. A league source refuted the report, saying the Cavs had not made one call about trading him. Waiters said before the game he did not ask to be traded. "I don't know what is going on," he said. He disputed the reported "three-hour meeting" he supposedly had with Cavs general manager Chris Grant. "That's nonsense," he said. ... Former Ohio State C Greg Oden has yet to appear in a game for the Heat. "He's coming along well, very well," Miami coach Erik Spoelstra said. "We're very impressed with the progress he's made." Oden hasn't played since 2009, and there is no timetable for his return. ... Cavs G/F C.J. Miles missed his third consecutive game due to a strained right calf muscle. Undrafted rookie Matthew Dellavedova started the past three games at Shooting guard. ... Heat F Shane Battier was held out of the game because of a cold. F Rashard Lewis made his first start of the season.