With 25.1 seconds left and Cleveland trailing by a point, Love threw the ball away on an inbounds pass; Kent Bazemore stole the ball and laid it in with 21.9 seconds to go for a 123-120 advantage.
James recorded a triple-double with 32 points, 16 rebounds and 10 assists before he fouled out in overtime.
James finished the game sitting on the baseline, removed from his teammates on the bench.
Paul Millsap's three-pointer with 1:12 remaining in overtime gave the Hawks their first lead of the game at 118-116.
The defeat dropped Cleveland, at 51-29, back into a tie with the Boston Celtics for the top seed in the Eastern Conference, although the Cavaliers own the tiebreaker.
The Hawks were without five key players when they beat the Cavs 114-100 in Cleveland on Friday.
"I don't know when that hits throughout the season, but March wasn't pretty for us", he said, recalling a 7-10 month. Cleveland was 2 of 14 from 3-point range in the first quarter on Friday. It was 65-46 at halftime and 93-67 after three quarters.
The Cavaliers committed a whopping nine turnovers in the fourth quarter and allowed 44 points as their defense continues to be a problem area.
"We didn't get any stops and they went on a 9-0 run to start the quarter".
For James, the explanation was simple. We got stops and we just walked the ball up the floor and that put us in one-on-one situations.
"When you let a team stick around, this is what happens. We guarded, competed at the end of the game to get ourselves back in it". "We've had some good moments and some not-so-good moments - like today". It was a questionable call and one that King James did not approve of. There's a darn good chance Boston steals this No. 1 seed, which is much more important to them than it is to Cleveland.
LeBron getting whistled for a five-second violation with 18.7 to play in the fourth and Kyrie getting tied up in the corner with under five seconds remaining all contributed to the Cavaliers Sunday afternoon collapse.
Cavs 102, Hawks 97 just because that feels likely. Cleveland had a 26-point lead heading into the fourth quarter.
"You expect for us to want to get better, and we were doing that and we took a couple steps back tonight", James said.
Atlanta faces the East-leading Cavaliers again on Sunday holding the No. 5 spot in the conference standings.
Toronto 110, NY 97: DeMar DeRozan scored 35 points and the Raptors beat the Knicks in NY to wrap up at least the No. 3 seed in the Eastern Conference.
That said, the Celtics, Raptors, and now the Hawks are teams to watch against the Cavaliers, but again, a seven-game playoff series is another story for those teams, including the Celtics.
Kevin Love would then make 1-of-2 free-throw attempts to extend the lead to 120-118 with less than one minute remaining in overtime.
Mike Dunleavy added 20 for Atlanta and got a little revenge against the Cavs, who tossed him in as part of a trade for Kyle Korver in February. This underscores the record-breaking performance of the Cleveland Cavaliers that makes them a shoo-in for the playoffs, and possibly another National Basketball Association title this season.