With both teams resting most of their stars in preparation for a playoff push, Sasha Pavlovic scored a game-high 16 points to help Boston earn a 78-66 victory over the Heat at TD Garden.
Rajon Rondo, Ray Allen and Kevin Garnett all sat out for the Celtics, while Miami's "Big Three" of LeBron James, Dwyane Wade and Chris Bosh also enjoyed the game from the sidelines.
Paul Pierce did start for the Celtics but played just under 18 minutes and finished with eight points. Marquis Daniels added 13 for Boston, which is locked into the fourth spot in the East but trail Atlanta by one game for home court advantage in the first round after the Hawks also won on Tuesday.
Boston will host Milwaukee on Thursday and can claim home court advantage with a win and an Atlanta loss to Dallas that same day as the Celtics hold the tiebreaker over the Hawks.
Dexter Pittman led the way for Miami with 12 points and James Jones added 11 in the loss, securing the top spot in the East for Chicago as it holds a 2 1/2 game lead over the Heat, who are locked into the second position.
Miami held a 10-point lead at the midpoint of the third, but the Celtics reeled off ten straight points to tie the game at 46-46 and the teams went into the fourth locked at 50-50.
The Heat registered the first bucket of the fourth, but Boston responded with a 15-4 swing to take a 65-56 edge with 4:44 left in the contest.
Miami cut it to five less than a minute later before the Celtics blew the game open with 13 straight points to take a 78-60 lead with one minute left.
"These games are still important," said Boston head coach Doc Rivers. "We know our rotation but someone's always going to help you in the playoffs."
Earlier in the game, Boston trailed 17-10 at the end of one quarter after turning the ball over 11 times and shooting 4-of-17 from the field.
An 8-0 start to the second found the Celtics on top by one before Jones buried back-to-back three-pointers to restore a 23-18 edge, and the Heat took a 34-28 lead at the break.
Two free throws had Boston within four to open the third, but Mike Miller connected on two three-pointers in just over a minute to press the lead to 42-32 less than three minutes into the third.
The Heat are winless in nine straight trips to Beantown, last winning there on April 6, 2007...The Heat will close out the regular season in Washington on Thursday...Allen sat out for a eighth straight contest due to a sore ankle...Miami failed to register a single fastbreak point, while the Celtics accounted for 14.