Irving, who added 10 rebounds, sent the game into OT by sinking a difficult jumper with 20.9 seconds left in the fourth quarter. The guard's performance helped overcome 34 points and 16 rebounds by Philadelphia's Joel Embiid.
Jayson Tatum added 23 points and 10 rebounds for Boston. Marcus Morris also scored 23.
Jimmy Butler added 24 points for Philadelphia, JJ Redick had 17 points, and Ben Simmons contributed 11 points, 14 rebounds and eight assists. Redick missed a shot that would have won the game at the end of regulation.
Lakers 127, Warriors 101
Kyle Kuzma scored 19 points and visiting Los Angeles ended a seven-game losing streak against Golden State.
Ivica Zubac had 18 points and 11 rebounds and LeBron James had 17 points and 13 rebounds before leaving with a groin injury in the third quarter. Reports afterward indicated that James avoided serious injury.
Rajon Rondo had 15 points and 10 assists off the bench, Brandon Ingram scored 14 points, Josh Hart had 12 points and fellow reserve Lance Stephenson finished with 11 points for the Lakers. Andre Iguodala scored a season-high 23 points for Golden State.
Rockets 113, Thunder 109
James Harden recorded his seventh consecutive 30-plus-point game, but when he needed scoring help down the stretch, he got it as Houston rallied for a win over visiting Oklahoma City.
However, a crucial stretch came with Harden either on the bench or facilitating, as the Rockets flipped an 88-86 deficit entering the fourth quarter into a 102-95 lead before Harden scored more than halfway through the final period.
Clint Capela (16 points, 23 rebounds) threw down a pair of dunks before Eric Gordon (17 points) converted a driving layup that extended the Houston lead to seven points. Austin Rivers, one day after signing with the Rockets, subsequently drilled a pair of 3-pointers to keep the Thunder at bay. Oklahoma City got 28 points and 14 rebounds from Paul George plus 21 points, nine rebounds and nine assists from Russell Westbrook.
Jazz 117, Trail Blazers 96
Donovan Mitchell scored 19 points to lead seven players in double figures as Utah breezed to victory over visiting Portland for the second time in four days.
Rudy Gobert collected 18 points, 14 rebounds and seven blocked shots as Joe Ingles and Dante Exum scored 15 points apiece for Utah, who went 13 of 29 from 3-point range.
Damian Lillard scored 20 points for the Blazers, who shot 39.3% from the field. Lillard scored only four points after intermission. Portland's next-highest scorer was Evan Turner, who came off the bench for 12 points.
Bucks 109, Knicks 95
Giannis Antetokounmpo scored 11 of his 30 points in the third quarter as Milwaukee seized control and recorded a victory at New York.
Antetokounmpo recorded his 13th 30-point game of the season and added 14 rebounds for his 22nd double-double, but it was his performance in the third that helped the Bucks get a win in their first appearance on Christmas since facing the Kansas City Kings in 1977. He also became the first Milwaukee player to score 30 on Christmas Day since Kareem Abdul-Jabbar in 1972.
Milwaukee, which got 20 points from Brook Lopez, won for the fifth time in six games overall. Rookie Kevin Knox scored 21 points for the Knicks.