Boston beat the Pistons for the first time in three meetings this season.
Detroit had rallied from 21-points down to win in Boston on Dec. 18, but the Celtics were able to hold off the Pistons each time they rallied down the stretch this time.
After going 2 for 14 from 3-point range in the first half, the Celtics made five from beyond-the-arc in the first 6 minutes of the third quarter.
Smith pulled Detroit to 69-63 on a 3-pointer with 7:27 left in the period, the Green made back-to-back 3s followed by another from Bayless to stretch Boston's lead to 78-63. The Celtics finished the period with eight 3s and led 95-84 entering the fourth.
Monroe's three-point play with 9:28 remaining cut Boston's lead to 97-89, then Bynum pulled up for a jumper on a fast break to get the Pistons within six.
Detroit stayed within reach and pulled to 113-109 on two free throws by Bynum, but the Pistons had to foul and Humphries sealed it by making two from the line.
The Celtics shot 50 percent in the second quarter and led by 13, but Detroit closed the half on a 9-2 run to pull within 57-49 at the break.
NOTES: Drummond's 45 double-doubles are most for a Detroit player since Isiah Thomas had 47 in 1985-86. ... Humphries' previous high this season was 19 points. ... Rondo reached 4,101 career assists, passing Bill Russell (4,100) for fifth place in team history. ... Boston finished with just seven turnovers.