With the Lakers down 15 points at one stage, the visiting side rallied to mount a comeback at the State Farm Arena as James nearly notched up a triple-double, finishing with 10 rebounds and nine assists to go with his season-high 47 points.
His previous best this season was 39 points against the San Antonio Spurs last month.
He ended the game with some of the Atlanta crowd chanting, "MVP!"
"Just awesome man, he's put the team on his back and been doing what he's done for the last 20 years. A hell of a performance," coach Darvin Ham told reporters when asked about James, who was playing his third game in four nights.
"Dropping 47 (points) is inspiring because he plays the game the right way... He motivates and inspires the team to go out there and do their jobs."
Only two other players have scored more points in a game after turning 38, with Michael Jordan and Jamal Crawford netting 51 points each.
