The Houston Rockets posted a sixth win in a row as they toppled the Toronto Raptors 107-95.
James Harden finished with 35 points – a 39th consecutive game in which he has scored 28 points or more – while Gerald Green added 18 off the bench.
Toronto's loss marked the end of a seven-game winning streak at home.
Gordon Hayward had 30 points off the bench as Boston took control early on in the game, leading by 25 points at half-time.
Kyrie Irving added 19 points and 11 assists for the Celtics, who had started the game having lost five of six since the All-Star break.
JJ Redick had 19 of his 26 points in the first half as the Philadelphia 76ers beat the Orlando Magic 114-106.
The Sixers led for most of the game, but Orlando came to within a point late in the fourth quarter.
Jimmy Butler helped push Philadelphia ahead in the dying minutes, while Mike Scott sank a three-pointer to extend the advantage with 48.6 seconds remaining.
The Bulls closed the gap after trailing by as much as 16 in the first half, before eventually falling short and recording their fifth loss in a row to the Pacers.
Elsewhere, Mike Conley recorded a career-high 40 points to help the Memphis Grizzlies edge the Portland Trail Blazers 120-111, while Karl-Anthony Towns led on 41 points as the Minnesota Timberwolves defeated the Oklahoma City Thunder 131-120.