Orlando saw red when he saw JB, who is reported to have got close to his ex-wife, model Miranda Kerr, shortly before they split in October last year.
The incident, at the Cipriani restaurant on the White Isle, was over before it began after entourages from both parties intervened and separated the pair.
A source told The Mirror: “Orlando was clearly annoyed when he saw Justin and instigated the situation by taking a swing at him.
“Luckily for both of them Justin ducked so Orlando’s punch missed.
“Within seconds people intervened and there was some minor pushing and shoving between their entourages.
"They were eventually separated and Justin, who was being cordial, stayed for a while longer outside the restaurant without incident.”
Miranda Kerr and Orlando Bloom pictured before their split
Justin and Miranda are said to have become close after meeting at the 2012 Victoria's Secret fashion show in New York.
Shortly after the altercation with the 'Pirate Of The Caribbean' star, the 'Baby' singer posted a snap of Aussie model Miranda on his Instagram page, which he later deleted.
We have a feeling Orlando might have something to say about that.
Watch the video of the incident above.