Al Horford has agreed to a two-year, $20 million contract extension with the Boston Celtics, his agent Jason Glushon of Glushon Sports Management told ESPN.

The new deal kicks in for the 2023-2024 NBA season and runs through Horford's 39th birthday. The former No. 3 overall pick in the draft is currently in the final season of a four-year contract he initially signed with the 76ers.

Horford will earn $26.5 million this year, according to ESPN.

CLICK HERE FOR MORE SPORTS COVERAGE ON FOXNEWS.COM

Al Horford reacts after scoring

Al Horford, #42 of the Boston Celtics, reacts after scoring a three-point basket during the first quarter of an NBA game against the New Orleans Pelicans at Smoothie King Center on November 18, 2022, in New Orleans, Louisiana.  (Photo by Sean Gardner/Getty Images)

Horford opted to leave Boston in the summer of 2019 for a more lucrative offer from the 76ers. He returned to the Celtics in 2021.

The 36-year-old has enjoyed somewhat of a career revival in his second stint with the Celtics. He played an important role during the team's run to the NBA Finals.

LAKERS’ PATRICK BEVERLEY ON DEANDRE AYTON SHOVE: ‘I WOULD DO THE EXACT SAME THING’

The veteran center has remained a productive player in the latter stage of his career. Horford a second-team All-Defensive team selection in 2018.

Boston Celtics player Al Horford plays defense

Washington Wizards center Montrezl Harrell, left, drives to the basket against Boston Celtics center Al Horford (42) during the second half of an NBA basketball game, Wednesday, Oct. 27, 2021, in Boston. (AP Photo/Charles Krupa)

Horford appeared in 141 postseason games without winning a conference championship. That streak ended last season when the Celtics defeated the Miami Heat in the Eastern Conference Finals.

The five-time All-Star is averaging 10.9 points and 6.3 rebounds this season. Starting center Robert Williams III has missed time this year due to an injury.

PRINCE WILLIAM CHARMS THE LADIES AS THE ROYALS RECEIVE MIXED REACTIONS AT BOSTON CELTICS GAME

After he signed with the Philadelphia 76ers in 2019, Horford was traded to Oklahoma City in 2020. The Celtics went on to reacquire him in 2021.

Al Horford defends against Giannis Antetokounmpo,

Milwaukee Bucks forward Giannis Antetokounmpo (front), of Greece, drives past Boston Celtics center Al Horford, top, in the second half of Game 1 in the second round of the NBA Eastern Conference playoff series, Sunday, May 1, 2022, in Boston. (AP Photo/Steven Senne)

Horford spent his first nine NBA seasons with the Atlanta Hawks before leaving in free agency for Boston in 2016.

CLICK HERE TO GET THE FOX NEWS APP

The Celtics now have 11 players under contract for the 2023-2024 season. Grant Williams is set to be a restricted free agent in July after he and Boston failed to agree on the terms of a contract extension.