Irving, who forced the OT on a jump shot with 20 seconds left in the fourth, also pulled down 10 rebounds for the Celtics, who trailed 113-108 with 3:33 left in the extra period before rallying behind Irving down the stretch.

Ben Simmons’ two free throws with 2:15 left to put the Sixers up 114-112, but Philadelphia didn’t score again.

Irving’s 3-pointer with 3:01 left gave Boston its first lead of overtime at 115-114, then after a miss by Philadelphia, Irving hit another 3-pointer with 1:28 left and Boston fans leaped to their feet and cheered louder than they had all night.

Jayson Tatum and Marcus Morris scored 23 apiece for Boston and Terry Rozier had 10 points.

Joel Embiid led Philadelphia with 34 points, making 12 of 12 free throws, and pulled down 16 rebounds. Jimmy Butler scored 24, JJ Redick had 17 points and Ben Simmons added 11 points, 14 rebounds and eight assists for the Sixers.

The Celtics led 57-51 at halftime, but Philadelphia used a 15-2 run in the third while shooting 60 percent in the period and led 89-86 entering the fourth.

Philadelphia shot 60 percent in the third quarter, hitting five 3-pointers, and led 89-86 entering the final quarter.

It stayed tight through the end of the fourth. Chandler got open for a 3-pointer with 37 seconds left and the Sixers led 108-106, then Irving pulled up for a 13-foot jumper to tie it at 108 with 20 seconds left.

Redick missed a jumper just before the buzzer and the game went into OT.

LACK OF OTs

This was only the second game on Christmas Day since 2004 that went to overtime. Miami’s win over New Orleans in 2015 was the only other one.

TIP-INS

76ers: Wilson Chandler returned after missing Saturday’s win over Toronto with a left quad contusion. He finished with 15 points . Philadelphia reserves did not score a point in the first half. . Redick got a technical after he was called for a foul with 7:32 left in the third. Irving made the free throw to put Boston up 70-63. . G Markelle Fultz traveled with the team but did not dress. Fultz, the No. 1 overall pick in the 2017 draft, has missed the last 15 games with thoracic outlet syndrome.

Celtics: Irving had 16 points and five rebounds in the first quarter. . C Aron Baynes (broken finger) missed his third straight game. . Horford’s minutes restriction was increased from 20 to 25 minutes in his second game back since missing seven in a row with a sore left knee.

UP NEXT

76ers: At Utah on Thursday night.

Celtics: Visit Houston on Thursday night, the first of three straight on the road.