The deal can’t be officially announced until Monday as the league observes its one-week free agency negotiating period.
Brown, 29, earned NBA Finals Most Valuable Player honors in helping the Celtics to the crown in 2024.
He is coming off a career season in which he averaged 28.7 points, 6.9 rebounds and 5.1 assists per game to keep the Celtics in contention despite the absence of star teammate Jayson Tatum as he recovered from an Achilles injury.
But Brown’s future in Boston was thrown into question when the Celtics reportedly attempted to trade him to Milwaukee as part of a deal for Giannis Antetokounmpo — who eventually landed in Miami.
“Saying goodbye isn’t easy when you’ve put your heart into something,” Brown wrote. “I’m big on respect and actions speak louder than words. To the people of Boston, thank you.”
He also had words for new fans and teammates in Philadelphia, where he’s been the enemy for years.
“Every city has its own identity, its own passion, and its own expectation,” Brown said. “I respect that, and I’m looking forward to earning that respect the only way I know how — through the work.”