Cedric Maxwell made one of two free throws, breaking a tie with 15 seconds left, and Robert Parish's one of two gave Boston its victory in Milwaukee.
After Maxwell's free throw gave Boston a 99-98 lead, new Bucks guard Phil Ford missed a 17-foot jump shot from the right side of the lane. Parish was fouled as he grabbed the rebound and made one of his two free throws.
The Bucks called time, but Steve Mix's inbounds pass was intercepted at midcourt.
The Bucks, who trailed by 16 late in the second quarter, came back to go ahead, 94-90, then were held scoreless for 5:41. A basket by Parish, one by Larry Bird, who had 20 points, and two free throws by Maxwell pulled the Celtics to a 98-96 lead.
Bob Lanier tied for Milwaukee on a tipin with 1:08 left and the Bucks had a chance to go ahead with 46 seconds left, but Lanier missed two free throws. Moncrief grabbed the rebound, and was called for traveling.
That led to Maxwell's tie-breaking free throw.
Marques Johnson had the flu and did not play for the Bucks. They were led by Sidney Moncrief's 22 points.