Bieber was in town for Game 3 of the finals between the Cleveland Cavaliers and Golden State Warriors.
The trouble began when Bieber arrived at his hotel shortly after the game ended at about 11 p.m.
No one knows what triggered the dust-up, but in a video obtained by TMZ, the singer can be seen squaring off against a much bigger man.
Bieber’s bodyguards tried to break up the melee. A spokesman for the Cleveland Police Department says cops were not called to the scene.
On Thursday afternoon, a shirtless Bieber posted an image on Instagram showing no bruises to his body.