James made a twisting bank shot with 19.3 seconds left to put Cleveland ahead to stay and the Cavaliers defeated the 76ers 91-88.
James, who finished with 26 points, took the ball at the top of the key, drove through the lane and put Cleveland up 90-88. After a Philadelphia miss, Cleveland forward Joe Smith was fouled and made one free throw.
Andre Iguodala, who led the 76ers with 19 points, missed a 3-pointer at the buzzer.
James made 4-of-17 shots and scored 13 points in Saturday's 85-71 loss to Detroit. The NBA's leading scorer answered his poor game less than 24 hours later. James was 11-of-18 from the field with nine rebounds and nine assists.
James' performance was no surprise to Philadelphia coach Maurice Cheeks.
"That's what superstars do," Cheeks said. "They rarely have two bad games in a row. He has a tough game in Detroit, came back and played the way he's capable of playing. That's why the superstars play."
James patiently dribbled beyond the foul line before heading into the lane for his winning shot.
"The plan was to attack, but I didn't think it was there in the beginning so I backed up," he said. "I was able to get it off the backboard."
James, with some help from Delonte West, also contested Iguodala's attempt to tie the game.
"I thought LeBron did a heck of a job getting through the screen and contesting the shot without fouling," Cavaliers coach Mike Brown said.
"I felt like I got a decent shot and I had a chance," Iguodala said. "It just didn't go down."
The news wasn't all good for the Cavaliers, whose grip on the fourth seed in the Eastern Conference has been slipping thanks to a three-game losing streak and seven losses in nine game going into Sunday.
Cleveland played without forward Ben Wallace, who missed the game because of back spasms. Wallace left Saturday's game in the third quarter after missing the two previous contests. Cleveland's injury problems continued when guard Daniel Gibson left the game in the third quarter because of soreness in his left ankle. He returned to the lineup after missing 18 games because he sprained the ankle on March 29.
Trailing 86-82, Cleveland got two 3-pointers from West to tie the game at 88 with 1:13 to play. West, who missed Saturday's game with a strained tendon in his left ankle, finished with 18 points.
"It's funny because it goes to show how mental this game actually is," said West, who also had 11 assists. "I remember sitting on the bench right before we came out from as timeout. I'm thinking 'I'm getting ready to hit it. I'm going to sting them.' Sure enough, the ball came right to me and I let it fly."
"Obviously, that put them over the hump," Cheeks said of West's big shots.
James was happy to see one of his teammates knock down some open shots.
"I attract a lot of double teams and one thing he has to do is catch and shoot," James said. "He doesn't have to think about it. That's what he did."
The surging 76ers lost consecutive games for the first time since Feb. 1-4 and remained a half game behind Toronto for the sixth playoff spot in the East. Philadelphia has won seven of 10 and went 11-4 in March.
"It was a tough loss for us," Cheeks said. "To play Cleveland like this, with LeBron, it's like playoff basketball."
"That's a very good team," James said. "This month they were the second best team in the whole NBA. It's a very good, high-flying athletic team."
Philadelphia controlled the first half, leading by as many as 11 points. The Cavaliers took their first lead, 53-51, on Devin Brown's 3-pointer with 7:26 left in the third quarter. The scored was tied 68-68 after three quarters.
Mike Brown benched shooting guard Sasha Pavlovic, who is 15-of-47 from the field in his last five games and started Devin Brown. Pavlovic, who has started 44 games, did not play. ... Miller added nine assists. ... The teams meet again in Philadelphia on April 14.