Adrian Wojnarowski of The Vertical first reported the news.
The NBPA is led by Michele Roberts and a nine-player leadership group, with Los Angeles Clippers point guard Chris Paul currently serving union president.
According to the organization's official website, the NBPA ensures "that the rights of NBA players are protected and that every conceivable measure is taken to assist players in maximizing their opportunities and achieving their goals, both on and off the court."
The group also assures the NBA owners meet their obligations to players under terms of the collective bargaining agreement and various other services ranging from protection of medical benefits to appealing fines and/or suspensions.
Anthony is one of the NBA's longstanding stars, having been in the league since 2003. He's been named to nine All-Star teams and two All-NBA Second Teams in his career. His ability to work with some of the sport's biggest stars to protect the present and build for the players' future seems like a logical next step.