Media mogul James Packer, 46, and Channel Nine TV boss David Gyngell, 47, were caught trading blows on camera by passers-by outside the former's Bondi Beach mansion in Sydney, reported Metro online.
Packer was reported to be angry his former best man has used camera crews to follow him and 31-year-old Kerr, ex-wife of British actor Orlando Bloom.
Gyngell is said to angry that Packer, who recently split from his second wife Erica Baxter, has become close to the Aussie underwear model.
Bondi resident Chris Walker claimed the pair 'went at it hammer and tongs'.
"Packer packered (sic) a punch but copped a couple of hits straight to the jaw... Then they all fell on the concrete fence and I think the other guy broke his face. They were looking for teeth after he left," Walker posted on Facebook.