Tatum scored half of his 14 points in the fourth quarter to help Boston win its sixth straight and beat the Nets for the eighth consecutive meeting.
The Nets held an 83-82 lead on a finger-roll layup by Spencer Dinwiddie with 91 seconds remaining, but 15 seconds later, Tatum gave Boston the lead for good on a driving dunk.
After Dinwiddie missed a floater with 55.8 seconds left, Boston's Kyrie Irving missed a layup but snatched the rebound from Brooklyn forward DeMarre Carroll and fed Tatum, who hit a corner 3-pointer with 45.7 seconds to play for an 87-83 lead.
A put-back layup by Brooklyn's Joe Harris with 36.9 seconds left made it 87-85, and the Nets had another chance to tie or win after Irving missed a floater with 21.3 seconds left. Dinwiddie and Harris missed layups before the Nets called their final timeout.
After Rondae Hollis-Jefferson and Carroll missed potential tying shots, the game ended when Hollis-Jefferson missed a tip-in just before the buzzer.
Irving led the Celtics with 21 points but shot 8-of-22 as Boston finished at 37.8 percent (37-of-98). Tatum recorded a career-best six blocked shots as Boston had 13 blocks while playing without Al Horford (sore left calf).
Dinwiddie scored 20 points on 7-of-15 shooting for the Nets, who shot a season-worst 33 percent (30-of-91) and missed 25 of 31 3-point attempts. Reserve center Jahlil Okafor added 12 points in his third game with the team while Joe Harris posted a double-double with 10 points and a career-best 12 rebounds.
The Nets (15-24) held a 41-39 lead at halftime and upped it to 50-43 early in the third. Irving scored seven points in a 15-2 run to give Boston a 58-52 lead with just under five minutes left in the third, and the Celtics (33-10) held a 64-61 lead into the final quarter.
--Field Level Media
Boston | Brooklyn | |
Kyrie Irving 21 | Scoring | Spencer Dinwiddie 20 |
Kyrie Irving 4 | Assists | Spencer Dinwiddie 3 |
Daniel Theis 10 | Rebounds | Joe Harris 12 |
Kyrie Irving 3 | Free Throws Made | Spencer Dinwiddie 5 |
Marcus Smart 3 | Steals | Jarrett Allen 1 |
Jayson Tatum 6 | Blocks | Tyler Zeller 3 |
Team | Points | FG% | 3PM-3PA | FTM-FTA | Assists | Rebounds | Blocks | Steals | Turnovers |
Boston | 87 | 37.8 | 5-18 | 8-15 | 12 | 44 | 13 | 8 | 5 |
Brooklyn | 85 | 33.0 | 6-31 | 19-22 | 11 | 55 | 11 | 2 | 18 |