The Celtics won a division crown for the 30th time in franchise history, fighting off the Magic thanks in large part to 14 assists from Pierce.
Orlando rallied from a nine-point, fourth-quarter deficit to climb within two on a dunk by Glen Davis with 32 seconds to go. Pierce then hit a jumper at the end of the shot clock and, after Jameer Nelson again brought the Magic within two, Pierce hit two free throws with 3 seconds left to clinch it.
Rajon Rondo, who has had at least 10 assists in 23 straight games, missed the contest with a sore back. That streak of 10 assist games is the NBA's longest in 20 years.
Davis scored 27 for the Magic and Nelson had 21. Orlando slipped a game behind Atlanta into sixth place in the Eastern Conference standings.