The Celtics clinched the Eastern Conference title with a 4-3 series win and will face the Golden State Warriors in the NBA Finals.
Tatum was drafted after Boston lost the 2017 Conference Finals before being part of the Boston side that lost at the same stage in his rookie year in 2018 and in 2020, scored 26 points, 10 rebounds and six assists for the game.
“It’s a great honour,” Tatum said after the game. “This is some of our fourth time in the Conference Finals.
“This is my third time. To get over this hump with this group means everything.
“I couldnt be prouder of these days. The road that we took to get here, not a lot of people believed in us. We took the toughest route and it worked out.”
Tatum wore a purple armband to tribute to the late Kobe Bryant throughout the game.
“Its Game 7,” he explained. “Everybody knows how much he means to me. my idol and my favourite player.
“To have something to show to him in the biggest game of my career so far and it worked out.”
The Celtics had been three games below .500 in January, marking a remarkable turnaround in the second half of the season.
Boston claimed a wire-to-wire win but they almost let a 13-point lead with under four minutes to play, as Jimmy Butler had a three-point attempt in the final minute which missed that wouldve put the Heat ahead 99-98 after a run.
Butler, who played practically every minute of the game, finished with 35 points with nine rebounds, while Bam Adebayo added 25 points with 11 rebounds.
Marcus Smart scored 24 points with nine rebounds and five assists, while Jaylen Brown, who has been part of all four Celtics sides that reached the Conference Finals, added 24 points.
Brown said: “It means everything all the adversity, all the struggles, the losses, the wins, we finally got to this moment, it makes it that much more special.”