In newly released video footage, the pop artiste, 22, can be seen punching a man in the face after he lightly taps the Canadian singer on the side of the head.
Rather than do the wise thing and back down, the 5’7 star channels his inner Scrappy Do and launches at the man – and things escalate quickly.
The footage, obtained by US website TMZ, was shared on Snapchat on Wednesday night.
It was filmed on Wednesday night outside the Sorry singer’s hotel in Cleveland, Ohio.
The clip – annoyingly grainy for people who have patiently waiting to see the mercurial singer get his comeuppance – shows several people trying to calm down and stop the fight, but poor Bieber still ends up losing.
Not only is there a lot of pushing and shoving, but Justin ends up squashed against some glass doors before being forced on to the ground.
It’s not known what sparked the fracas, or the identity of the other man involved in the fight.
Justin was in town for the third game of the NBA Finals, and was representing the home town heroes in a Cleveland Cavaliers shirt – so perhaps the row was triggered by standard post-game trash talk.