He had 45 points and made eight threes on 12 attempts.
James reached his latest triple-double in regulation and finished with 32 points, 16 rebounds, and 10 assists.
"It was a tough loss right here", said LeBron James, who finished with a triple-double but fouled out in overtime. His three at the 7:22 mark gave Cleveland its first double-digit lead. Paul Millsap ended up with the ball after a jump ball and hit a buzzer beater to send the game to overtime all tied at 111.
The Hawks have clinched a playoff berth in the Eastern Conference for the 10th straight season.
In the last three meeting between Cavaliers vs Hawks in this National Basketball Association season, the Cavs have won only one match. Lue said that his players did not respect Atlanta's reserves and letting them hang around for three-plus quarters gave them confidence. They are more methodical than flashy, yet they get the job done more often than not and have been rewarded with another trip to the postseason.
Cleveland was ahead 65-46 at halftime and in control as Irving had 19 points.
But it unravelled for them in the fourth, as Atlanta scored the first nine points of the quarter to launch their comeback. Cleveland Coach Tyronn Lue did not have anything good to say after the game.
For James, the explanation was simple.
"We didn't get any stops and they went on a 9-0 run to start the quarter". "When you allow teams to stick around, that's what happens".
"There's five games left so we want to finish strong and finish with a positive note and wherever we end up in the play-off spots we will think about it then".
Crystal Palace close on survival after comeback earns draw
He said: "It has never happened where we have faced an opponent who has given him special treatment and been man-marked". We can score goals. "It's a fantastic point".
On the brink of quitting the Hawks have reminded everyone in the league that this is a force to be taken seriously, and what better way to show that than to stun the reigning conference champions twice in one week.
James said he wasn't concerned with the possibility of going into the post-season seeded behind Boston. He shot 4-of-14. The Cavs led in overtime by as many as five points and were still up three when James fouled out.
That certainly wasn't the case in the fourth quarter on Sunday. At times, like the first three quarters today, the Cavaliers look like an offensive juggernaut that few teams can hang with.
Turning Point - Those nine turnovers in the fourth quarter.
"Any time you beat the defending National Basketball Association champions, it's huge", Hardaway said, "no matter the circumstances". This was clearly a game Cleveland wanted to win and it didn't, a distressing sign considering what's at stake in the standings.
DeMar DeRozan scored 35 points as the Toronto Raptors clinched at least the third play-off seed in the NBA's Eastern Conference with a 110-97 victory over the New York Knicks on Sunday.
"Those games will get a whole bigger meaning at the end of the season with home-court advantage [on the line] which is what we are trying to accomplish here", Ilyasova added.
After Irving's two free throws with 10.4 seconds left pushed the margin back up to five points, Paul Millsap was fouled behind the three-point line and converted with 8.3 seconds left.
Cleveland erased a double-digit second quarter deficit to take a 67-58 lead with 6:54 left in the third quarter.
- If the Celtics win one of their final two games, and Cleveland loses out, the Celtics will have the one seed.