Jayson Tatum scored 31 points and pulled down 10 rebounds and Jaylen Brown added 28 points as six Celtics players scored in double figures and Boston cut the deficit in the best-of-seven Eastern Conference finals to three games to two.
Goran Dragic led the Heat with 23 points and Duncan Robinson added 20 for Miami, who are trying to reach the NBA finals for the first time since 2014.
With their season hanging in the balance, the Celtics exploded for 41 points in the third quarter to turn the tide in a game dominated early by Miami.
Under solid pressure from the Heat defense, the Celtics had made just one of their first 12 shots and connected on just five of 20 from the field in the first quarter.
Boston trailed by as many as 12 in the opening period, which ended with the Heat leading 26-18.
🏀 GAME 5 FINAL SCORE 🏀Jayson Tatum (31 PTS, 10 REB, 6 AST) and the @celtics use a huge 2nd half to win Game 5 and… https://t.co/pdkhGDEdG9
— NBA (@NBA) 1601090665000
Miami again built the lead to 12 in the second period and finished the first half with a 58-51 lead.
But Boston were beginning to see some shots fall, and as they turned up the intensity on both ends of the floor after the interval Miami had no answer.
The Celtics opened the second half with a 20-5 scoring run.
Marcus Smart’s three-pointer tied it up at 60-60 and Boston took the lead for the first time in the contest, 62-60, on Brown’s layup off a feed from Kemba Walker.
They wouldn’t trail again.
Walker’s three-pointer with 4:26 left in the third gave Boston a 10-point lead and the Celtics took a nine-point edge into the final frame, when they continued to pour it on.
Tatum scored 17 in the third and the Celtics out-rebounded the Heat 16-5 in the quarter.
“Leave it all on the floor.”@jaytatum0 discusses his mindset after the Game 5 win. NBA Playoffs Press Conferenc… https://t.co/g5T2BX1plH
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“We got back to playing Celtics basketball,” Walker said. “I felt like early in the game we were a little frustrated, bickering at each other at the refs. We got out of it, and just let the game come to us.”
The Celtics will try to build on their momentum against a Heat team determined to put them away in game six on Sunday.
The winners of the series take on either the Los Angeles Lakers or Denver Nuggets for the NBA title in the quarantine bubble in Orlando, Florida.
The Lakers lead the Nuggets three games to one in the Western Conference finals.
Boston’s German centre Daniel Theis contributed a double-double of 15 points and 13 rebounds, Smart finished with 12 points and Gordon Hayward chipped in 10.
“Boston played great in that second half, they deserved and earned what they got,” Heat coach Erik Spoelstra said.
“We did not compete hard enough defensively and we paid the price for that. But you do have to credit Boston, they played with great force particularly off the dribble.”
Spoelstra noted that the Celtics scored just four points in the paint in the first quarter but added: “It was just a deluge to the rim after that.”
Boston scored 30 points in the paint in the second half and had 13 fastbreak points to Miami’s zero after the break.
“We didn’t defend as well as we could in the first half and that’s what got our offense going in the second half,” Tatum said. “We just locked in, we were all on the same page.”