The Heat are within nine games of matching the record of 33 consecutive wins held by the 1971-72 Los Angeles Lakers.
James and his teammates have insisted the record isn't one of their goals, and for more than 30 minutes the defending champions seemed disinterested and on the verge of losing for the first time since Feb. 1. Miami trailed 67-40 with 7:44 left in the third quarter.
But behind the irrepressible James, who added 12 rebounds and 10 assists, the Heat inched closer to history by matching the biggest comeback in the NBA this season, according to STATS.
James had 14 points in the fourth as Miami completed its second straight comeback. The Heat rallied from 17 down — 13 in the fourth quarter — to beat Boston 105-103 Monday night and snap a tie with the 2007-08 Houston Rockets for the second-longest winning streak in NBA history.
Although the Cavs were missing All-Star guard Kyrie Irving, Dion Waiters and Anderson Varejao — their top three scorers — they pushed Miami to the limit.
It wasn't until James, playing his fourth game back in Cleveland since leaving as a free agent in 2010, made two free throws with 4.7 seconds left that Miami could relax a little. The Cavs had one last chance to tie it, but C.J. Miles was long with a 3-pointer in the final second, letting Miami off the hook.
Following the game, James stopped to sign a few autographs as he made his way to Miami's locker room. This was much tougher than he and the Heat could have imagined.
Mario Chalmers added 17 points and Dwyane Wade had 11 for the Heat, who outscored the Cavs 30-18 in the fourth quarter and 64-40 in the second half.
Wayne Ellington had 20 points and Tristan Thompson 18 for Cleveland, which went from a stunning upset to blowing the biggest lead in a loss in franchise history.
Down by nine to open the fourth, the Heat were up 95-86 with 3:02 left and seemed to have the Cavaliers on the ropes.
But Cleveland bounced back and closed to 96-95 on Thompson's two free throws with 44 seconds to go. Wade then missed a jumper, but Ellington misfired on a step-back 23-footer with 5.2 seconds to go.
James was fouled and the reigning MVP, with a sellout crowd of 20,562 roaring, stepped to the line and dropped both free throws to make it 98-95.
Miles was contested on his final shot, and once it clanked off the rim, the Heat headed home with a chance to extend their streak to 25 on Friday against Detroit.
This game had a little of everything, including a fan running on the floor in the fourth quarter. The young man was wearing a T-shirt that said: "We Miss You, 2014 Come Back," a reference to James' possible free agency and return to Cleveland, where he played seven seasons.
James patted the fan on the head as security rushed him off the floor.
The start of the game was delayed 35 minutes because of a spill on the floor caused by condensation from a carbon dioxide container inside the scoreboard.
James scored eight straight points to open the fourth, hitting a 3-pointer to tie it 77-all. He then turned toward the crowd and delivered an icy stare, his way of saying, 'OK, enough is enough.'
The Heat had to work extra hard for this one, but they may look back on the comeback as a defining moment.
Trailing by 27 — matching their biggest deficit this season — in the third quarter, the Heat were in major danger of getting blown out.
But Miami rallied and outscored Cleveland 28-10 in a 7-minute stretch to pull to 74-68 on Ray Allen's 3-pointer from the left wing. With Cavaliers fans holding their breath and swallowing hard, Daniel Gibson drilled a 3 just before the horn to put the Cavs up 77-68 heading to the fourth.
The Cavs led by 21 at halftime, a stunning development for a team that had to sign a journeyman guard earlier in the day just to have some depth.
Cleveland reeled off a 19-0 run and outscored Miami 23-3 over final 6:45 of the first half. As they walked to the locker room at halftime, the Heat had to be wondering what was happening and any thoughts they may have had of matching the Lakers' record were vaporizing quickly.
Downstairs, Cavs owner Dan Gilbert joked that he didn't know what was happening.
"I was out, what's the score?" he cracked.
James wasn't sure what kind of reaction he would get from Cleveland's fans. However, he was confident it would be nothing like his first visit here after he signed with the Heat in 2010.
"It can't get no worse than Year One, Dec. 2, 2010," he said, referring to the night Quicken Loans Arena was transformed into a cauldron of hate — directed at him. "It can't get no worse than that, so I'll be all right."
James has moved on and he believes Cleveland fans aren't nearly as mad at him as they once were.
Even Gilbert seems to have softened. Gilbert, who sent his infamous letter to Cavs fans ripping James on the night he announced he was signing with the Heat, went to his Twitter account to offer something of an olive branch to his former employee.
"Cleveland Cavaliers young talent makes our future very bright," Gilbert tweeted. "Clearly, LeBron's is as well. Time for everyone to focus on the road ahead."
James was standing at midcourt awaiting the opening tip when arena workers first noticed a pool of liquid on the floor. As ball boys tried to mop it up, the officials sent both teams to their locker rooms and the giant, fire-breathing, fog-spewing scoreboard was lowered to the floor so the problem could be fixed.
The team returned and warmed up for five minutes before the game got under way.
Once it began, the Cavs came out energized. Cleveland opened a 24-16 lead and was outhustling Miami's players, who swore they wouldn't overlook a banged-up Cleveland squad.
NOTES: The Cavs are going to wait a week before they evaluate Waiters, who has loose cartilage, and decide whether he needs surgery. Cleveland coach Byron Scott hopes his young guard comes back in the final month. "If he gets back, I'll be thrilled to death," Scott said. ... Miami's three wins over Cleveland this season have been by a total of nine points.