The Brooklyn Nets' national anthem singer took a knee for part of the song on Friday.
Justine Skye got down on one knee as she finished the anthem, and the crowd split into cheers and boos.
The NBA requires coaches and players to stand for the anthem.
A Nets representative said they were unaware she was planning to kneel during the game with the Orlando Magic.
"We recognize that tonight's national anthem singer kneeled briefly at the end of her performance and we were not aware that she was going to do so," the spokesperson said.
The NFL has been in the headlines as players across the league protest the national anthem by sitting, locking arms, or taking a knee as it is played before games. The league has said it will not require players to stand.