Rajon Rondo added 14 points and dished off 11 assists while Kendrick Perkins contributed 13 points and grabbed 14 rebounds as the Celtics, who saw their game-long lead evaporate in the fourth quarter, hung on for the win.
Boston held the Lakers scoreless for four minutes late in the final quarter while nursing a slim lead. Up 85-84 with 3:16 to go, Rondo connected on a driving layup off the glass for a 3-point lead.
Lamar Odom responded by hitting a basket with 2:18 left, but the Celtics' tough defense held Los Angeles, playing without all-star Kobe Bryant, scoreless the rest of the way.
Pau Gasol led the Lakers with 22 points and seven boards, while Ron Artest added 15 points and eight rebounds in the loss.