Amir Johnson had 12 points and 12 rebounds and Aaron Gray matched a season-high with 11 rebounds as the Raptors avenged a 100-64 loss at Boston on Feb. 1, their worst defeat of the season. James Johnson scored 14 for Toronto.
The Raptors, who snapped a three-game losing streak, had lost five of six coming in and were treated with a rare standing ovation from the crowd of 19,207 in the final minute.
The Celtics, who had won nine of ten before Thursday's overtime loss to the Los Angeles Lakers, lost back-to-back games for the first time since a five-game skid from Jan. 6 to 16.
Trailing 63-51, to begin the fourth, the Celtics were unable to mount a serious comeback. Allen's jumper cut it to 77-69 with 3:35 left, but Linas Kleiza answered with a 3-pointer. And after Garnett made one of two from the line to trim the deficit to 81-72 with two minutes left, Calderon hit a step-back 3 to push the lead back to 12.
Toronto started brightly, using a pair of running dunks by James Johnson and Calderon's alley-oop pass to DeRozan to open an 18-7 lead with 4:30 left in the opening quarter. DeRozan had nine points in the first, Calderon and Johnson had eight each as Toronto led 26-14 after one.
Boston made six turnovers in the first, but also had coach Doc Rivers fuming after failing to inbound the ball on one possession, forcing a timeout. Rivers yelled angrily at his team in the huddle before stomping back to the bench to let the players sort themselves out.
The Celtics closed the gap in the second, when Toronto made just four of 15 field goal attempts, but still trailed 41-34 at the break. Allen and Rondo combined for just two points in the first half, missing seven of eight shots.
The Raptors pulled away again in the third with DeRozan feeding Amir Johnson for an alley-oop to make it 61-45 with 3:52 left, matching their biggest lead of the game. Boston trailed 63-51 heading into the fourth.
NOTES: DeRozan has scored 20 or more in three of his past four games. ... The loss snapped Boston's season-high three-game road winning streak. ... Celtics G Avery Bradley (right shoulder) and F Sasha Pavlovic (left wrist) sat out for the second straight game. ... Toronto G Jerryd Bayless was unavailable after leaving Wednesday's loss to Milwaukee with a sore left ankle.