Kemba Walker scored 27 points as Boston beat the Oklahoma City Thunder 112-111 for the Celtics’ seventh straight victory.
Danilo Gallinari and Shai Gilgeous-Alexander each had 24 points for the Thunder in a game they led 61-52 at half-time.
Tatum acknowledged what a tough battle it had been to get a single point victory. “It took a lot of grit,” he told reporters after the game.
“They are a really good team. They are tough and they compete, so we just had to match their intensity.”
The Los Angeles Clippers gave the Cavaliers their worst ever home loss in a 133-92 rout in Cleveland.
Lou Williams scored 25 points and Paul George got 22 in a game the Clippers led all the way, despite playing without injured forward Kawhi Leonard.
The Cavaliers have now lost 12 straight games at home and 13 of 14 overall.
Furkan Korkmaz got 31 points and Joel Embiid scored 28 as the Philadelphia 76ers beat the Chicago Bulls 118-111 to improve their NBA-best home record to 24-2.
Zach LaVine scored 32 points and Luke Kornet added 25 for the Bulls, who have lost five straight.
The Sixers remain in fifth place in the Eastern Conference, while the Bulls are stuck in 10th.
In Washington, Ja Morant got 27 points, 10 assists and 10 rebounds for his first career triple-double to help the Memphis Grizzlies beat the Wizards 106-99.
Trae Young scored 48 points in Atlanta as the Hawks beat the New York Knicks 140-135 after two periods of overtime.
In Houston, Bojan Bogdanovic scored a three-pointer on the buzzer to give the Utah Jazz a 114-113 victory over the Rockets.
And in Portland, the Trail Blazers beat Miami 115-109 in the Heat’s third straight loss.