The fearsome sportsman and avid pigeon fancier will go public with his love for bird racing in new reality show Taking on Tyson, which premieres in America next month (Mar11) - and he insists he's always been a fan of his feathered friends.
And it was defending his passion as a child that first made him realise he was a fighter.
The Hangover star says, "I was nine or 10 years old, and I have 200 birds (sic). I showed the birds to people who I thought were my friends, and they got a bunch of guys to come and snatch my birds.
"One guy said, 'You want it?' There was blood on my face, and I tried to fight him. I was scared to death.
"I didn't really beat him up, but I hit him more than he hit me so I thought I won... That was the beginning of my fighting life."