The Hobbit star and the troubled pop idol were at a star-studded event at Cipriani restaurant when the two were caught on camera nearly coming to blows.
In footage obtained by TMZ, Bieber and Bloom get involved in an altercation that soon turns into a shoving match, and a voice which editors claim to be the singer is heard yelling: "What's up, b**ch?" in an attempt to egg Bloom on.
After the incident, Bieber reportedly left the party, which was also attended by Paris Hilton, Lindsay Lohan, and Sean 'Diddy' Combs.
It is not known what sparked the clash.
In 2012, rumours surfaced that Bieber was getting "too close" to Bloom's then-wife, model Miranda Kerr after a Victoria's Secret fashion show in New York City, and earlier this year, Bloom was spotted spending time with Bieber's ex-girlfriend Selena Gomez.