Paul Pierce scored 21 for Boston, which has lost three of its last four, and three of five at home. Kevin Garnett scored 13 points with 11 rebounds, and Ray Allen had 15 points for the Celtics.
Rasheed Wallace had 13 rebounds, but he was 0 for 8 from 3-point range and Boston was 2 of 19 from beyond the arc as a team to contribute to a 34.5 percent overall shooting percentage.
The game was the first meeting between the teams since the playoffs, when Orlando rallied from a 3-2 deficit to advance. It was the first time in franchise history that the Celtics lost a series after going into Game 6 with a chance to clinch.
Boston didn't have Garnett back then; he was recovering from a knee injury. And it didn't have Wallace, who signed in the offseason as a free agent.
Kendrick Perkins picked up his fifth foul - and a technical to go with it
- with 7:25 left in third and played only 15 minutes in all. Wallace took most of his minutes, hitting from under the basket with 2:53 left to tie the game 78-all.
But Orlando had a key addition, too: Carter, who hit a fadeaway jumper from 12 feet to break the tie with 2:33 to play. Lewis made a pair of free throws with 59 seconds left, then Jason Williams stole the ball from Ray Allen to clinch the victory.
The Magic scored 12 straight points after trailing 6-5, the Pietrus made a 3-pointer and a 19-footer at the end of the first quarter to make it a 16-point game. But Boston scored seven in a row to start the second, then went on a 12-3 run just before the half to make it a 41-40 deficit.
Orlando led by 10 in the third, and 66-59 heading into the fourth before Boston cut it to one point when Wallace had a steal, leading to Pierce's fast-break layup that made it 75-74 with 5:16 to play.
NOTES: The Celtics shot 33 percent in the first half. ... Carter passed Rick Barry and moved into 53rd on the career scoring list with a driving jumper with 9:34 left in the first half that made it 31-20.
