ATLANTA -- Kyle Korver said the Hawks owed the Celtics a big comeback.
This one was really big.
Korver scored 27 points, most on 3-pointers, and Atlanta overcame a 27-point deficit in the first half to beat Boston 123-111 in double-overtime on Friday night, handing the Celtics their sixth straight loss.
Boston's biggest lead came in the second quarter. Korver remembered the Hawks led by 19 points, also in the second period, before the Celtics rallied for an 89-81 win in Atlanta on Jan. 5.
"We had a good example of how to come back from what they did to us the last time," Korver said.
Jeff Teague had 23 points for Atlanta before fouling out in the first overtime. Al Horford had 24 points -- including seven in the second overtime -- and 13 rebounds. Josh Smith, who opened the second overtime with a three-point play, had 17 points and 14 rebounds.
The Celtics (20-23) fell three games under .500.
"It's definitely a tough pill to swallow," Paul Pierce said. "We've got to have some sort of discipline. That's the key word for us. It is cause for concern. We've got to come in with the mindset to play for 48 minutes."
Kevin Garnett had 24 points and 10 rebounds but fouled out in the second overtime as the Celtics were left with their longest losing streak in six years.
Rajon Rondo had 16 points, 11 assists and 10 rebounds for his fifth triple-double of the season.
"We had a chance to put this game away, man. We didn't do that," Garnett said. "We gave a team life. You can't do that.
"Korver came out, obviously got hot, and we couldn't turn it off."
Korver had all of his career-high eight 3-pointers in the second half, setting a franchise record, and five in the fourth quarter.
"When you make some shots, all of a sudden you get better screens and you get better passes," Korver said.
Korver's eighth 3, with 2:26 remaining in regulation, cut Boston's lead to 98-96. Horford's two free throws with 1 minute remaining tied the game at 98-all to set up the first overtime.
With the game tied at 105-all in the first overtime, Courtney Lee's steal from Horford set up Lee's two free throws to give Boston the lead, but Smith tied the game with a jam.
Pierce, who had 12 points, missed a jumper at the end of the first overtime.
"It seems we let our foot up off the gas," Rondo said. "We have to stay positive and continue to move forward and try to dig our way out of this hole."
The Hawks outscored the Celtics 16-4 in the second overtime.
Boston appeared headed for a rout when it led 48-21 in the second quarter.
"The most important part is how we didn't lay down in the second half," Smith said.
"We didn't get discouraged. We came out in the second half and played outstanding. ... We applied a little pressure and took the fight to them in the second half."
Atlanta trailed 57-38 at halftime following a modest recovery.
The Hawks' comeback gained strength as they outscored the Celtics 21-2 to open the second half, including a 19-0 run for a 59-all tie. Korver had three 3-pointers in the run.
The comeback was Atlanta's biggest since at least the 2000-01 season, according to STATS LLC.
"This is probably one of the most amazing comebacks I've been associated with," said Hawks coach Larry Drew, who said he was including his years as a player and a coach.
It was Atlanta's third straight win following four losses in five games.
"This was a very gutsy win for us," Drew said. "It shows what we're made of. It shows we have the ability to persevere."
The Hawks led 80-77 after Korver's fifth 3-pointer, but the Celtics regained the lead on back-to-back baskets by Pierce and Courtney Lee.
Horford started after missing one game with a sore left calf, and Devin Harris had 14 points in a backup role after missing two games with a sprained left ankle.
Milwaukee also rallied from 27 points this season to beat Chicago 93-92 on Nov. 23, 2012. ... The Celtics' last six-game losing streak was April 4-15, 2007 ... The 10 points were a season low for first-quarter points for the Hawks. ... Korver extended his streak of games with at least one 3-pointer to 37, the longest of career and longest active streak in the NBA. ... Hawks C Zaza Pachulia returned after missing one game with a sore right Achilles.