Boston Celtics star Jaylen Brown has agreed to sign the richest deal in NBA history -- a five-year, $304 million supermax contract extension, his agent, Jason Glushon, told ESPN on Tuesday.

Brown and Glushon met with Celtics management and ownership Sunday evening in Boston, finalizing the remaining elements of the historic deal that keeps the two-time All-Star under contract through the 2028-29 season.

Brown's deal exceeds two-time MVP Nikola Jokic's $276 million extension with the Denver Nuggets, an increase based on the rise in the salary cap and league revenue. Brown, 26, took a physical Monday in Boston to solidify the deal.

Brown became eligible for the five-year supermax extension with the Celtics upon earning second-team All-NBA honors in 2022-23. Brown and teammate Jayson Tatum, who is eligible for a supermax extension next summer, constitute one of the NBA's most productive duos and are cornerstones of the Celtics' championship contender.

Brown averaged career bests of 26.6 points and 49% shooting last season. He will make $31.8 million next season in the final year of his previous deal.

Brown is slated to make $52.3 million when the contract kicks in during the 2024-25 season and $69.1 million in 2028-29, the final year of the deal. He is not eligible for a no-trade clause because he signed an extension.

Tatum and Brown combined for 56.7 points per game last season, the fourth-most by a duo since the 1976-77 merger, according to ESPN Stats & Information research. They both also scored 30 points in 10 games, a feat only Shaquille O'Neal and Kobe Bryant have accomplished in the past 30 seasons. Brown progressed as a shot creator last season with 54% of his made shots unassisted -- a career-high 1.15 points per direct drive, according to Second Spectrum.

The Celtics have made the playoffs in each of Brown's seven NBA seasons, including the NBA Finals in 2022 and three Eastern Conference finals trips. Boston drafted the former UC-Berkeley star with the third overall pick in 2016.

Off the court, Brown is a businessman, fashion aficionado and mentor for countless kids, as well as a philanthropist in Boston and internationally. He currently serves as vice president of the National Basketball Players Association.

The Atlanta native recently attended Paris Fashion Week and spoke at Variety's Sports and Entertainment Summit about off-court success. He has been generating partnerships that build bridges to enable youth of color access to equal education and leadership opportunities through his 7uice Foundation.

Brown is currently hosting his third annual Bridge Program in Boston for 100 Boston public school students. He plans to also go to Kenya this offseason to speak with and mentor over 200 local students. Brown was also among 20 NBA players who took part in the NBPA's "The Sanctuary," a performance retreat for players hosted in Andalucía, Spain.

ESPN's Adrian Wojnarowski and Bobby Marks contributed to this report.