Paul Pierce had 21 points and eight rebounds for the Celtics (3-3), who pulled to .500 after losing their first three games of the season. Rookie Greg Stiemsma, making his first start, had 13 points and seven rebounds, and reserve Brandon Bass scored 12.
Andray Blatche led Wizards (0-5) with 28 points and nine rebounds, JaVale McGee had 17 points and 14 boards, and John Wall had 11 points. Head coach Flip Saunders didn’t see much of the game from the bench after he was ejected 1:46 into the contest.
Allen was 6 for 7 from beyond the 3-point line.
Boston beat the Wizards 94-86 in Washington on Sunday.
Celtics center Jermaine O’Neal was out with a tight left hamstring.
Allen’s fourth 3-pointer of the game, coming with 8:56 to play, pushed Boston ahead for good, 75-74. Bass then hit a foul-line jumper and, after a basket by the Wizards’ Nick Young, Rajon Rondo found Marquis Daniels cutting backdoor for a layup. He was fouled on the play and made the free throw, increasing it to 80-76.
Bass then nailed another jumper — this one from the right corner — and Rondo had a breakaway layup, increasing Boston’s lead to 84-76 with 6:21 to play.
The Wizards made one last run, closing it to 84-80 on Blatche’s three-point play, but Allen hit a jumper on the left wing and followed that 43 seconds later with a 3 from the right wing.
Allen’s third 3-pointer of the final quarter made it 95-87 with 1:30 to play.
Saunders was upset after Stiemsma blocked Rashard Lewis’ shot and knocked him to the floor as play continued. He got up off the bench and screamed at the officials to earn the first technical, then walked to midcourt still protesting to earn the second and an automatic ejection.
Washington led 70-69 after three quarters.
Neither team held more than an eight-point lead in the first half, and it changed eight times before the Wizards took a 48-47 advantage into halftime.
Notes: Boston coach Doc Rivers said he likes facing a team twice in a row. “I wish our league did it more. I’ve always said that,” he said before the game. “I think it builds competition.” … Wizards G Wall was whistled for a technical 4 minutes after Saunders. … Boston C/F Chris Wilcox returned after missing the previous three games with a bruised left shoulder. … Assistant Randy Wittman took over after Saunders was tossed.