Celtics forward Jayson Tatum yells after a dunk against the New Orleans Pelicans on Monday in Boston. Tatum had 27 points in the Celtics’ 104-92 win. Mary Schwalm/Associated Press

BOSTON — Jayson Tatum scored 27 points and the Boston Celtics erased an 18-point first-half deficit with a 104-92 victory over the New Orleans Pelicans on Monday.

Tatum scored 21 in the second half to help Boston rally for its fifth win in six games.

Dennis Schröder and Jaylen Brown each had 23 points, Al Horford scored 12 and Grant Williams 10 for Boston. Tatum and Brown each had eight rebounds and Schröder added nine assists with five boards.

“It was an early game and we didn’t come out the right way,” Schröder said of both the early afternoon tip-off and slow start. “At halftime, it was keeping everybody accountable and saying: ‘You’ve got to play with more energy.’ I think that’s what we did in the second half. We got easy buckets on the offensive end and shared the ball. ”

New Orleans center Jonas Valančiunas recorded his 30th double-double this season with 22 points and 14 rebounds. Herbert Jones had 16 points and Brandon Ingram had 15 points with 10 rebounds.

The Pelicans fell to 6-17 on the road.

Tatum slowly walked down the hallway from the locker room with the rest of his teammates for the start of the second half, then spurred a 22-7 run.

“It looked like we woke up at halftime a little bit,” Boston Coach Ime Udoka said. “Overall, the offense really woke up, playing with the pace we wanted to and taking care of the ball.”

Tatum hit a jumper and followed that with a conventional three-point play. He added a crowd-pleasing fast-break dunk after a steal and Aaron Nesmith had a baseline drive for a dunk, got fouled and made the free throw, putting Boston ahead 85-74 with 8:04 to play.

“The ball got really stagnant (for us) in the second half,” Ingram said. “That was definitely part of it in the fourth quarter. In the third, they made a little bit of a run and were really aggressive.”

The Celtics completely erased the large deficit, taking their first lead of the game on Schröder’s left-wing 3 late in the third quarter and led 71-69 entering the final quarter.

The Pelicans had opened a 42-24 lead with just over four minutes left in the second quarter and led 46-39 at halftime.

“Give credit to the Celtics,” New Orleans Coach Willie Green said. “I think they stepped it up in the second half.”

NOTES

PELICANS: Started fast and opened a 17-6 lead in the game’s initial six minutes. … They led by 12 points late in the second quarter despite shooting under 40%. … Josh Hart had a double-double with 14 points and 11 rebounds in his last game.

CELTICS: Robert Williams III was sidelined due to personal reasons. The 24-year-old revealed on Instagram that he’s preparing for the birth of a child. … Marcus Smart remains in COVID-19 protocol. … With Robert Williams and Smart out, Coach Ime Udoka inserted Grant Williams and Schröder into the starting lineup. … Brown was whistled for a technical in the second quarter. … They entered with an exact opposite home/away record. They were 14-8 at home and 8-14 away from TD Garden. … The Celtics missed 16 of their initial 18 on 3-point attempts with Brown, Romeo Langford and Nesmith putting up shots that didn’t even hit the rim. Nesmith’s hit off the side of the backboard.