Lewis Hawkins, 24, had just returned from an evening gym session when Dean Maundrell and Michael Bennett tried to drunkenly mug him.
They ambushed him as he parked his car but the strongman fought back, repeatedly punching Bennett and ignoring Maundrell’s empty threat that he had a gun.
Pumped-up Mr Hawkins then stood guard over Bennett as neighbours called police and Maundrell fled, only to be caught later.
Will Woodman, defending at Swindon Crown Court, said: 'They came up against the last person they should want to come up against - a cage fighter who knows how to look after himself.'
The court heard how Mr Hawkins was targeted as he pulled up outside his flat in the town after a training session in March.
He saw two men loitering in the unlit car park and Maundrell shouted 'Oi mate, what's the time? I'm not from Swindon' and then grabbed his arm.
Bennett appeared and the two men stood over him as he tried to get out of his Honda Civic.
Maundrell demanded 'Give me what you've got' and reached into Mr Hawkins' pocket and grabbed his car keys.
Bennett, 27, then took a swing at his intended victim but missed and was punched in the face in return.
The fighter went to walk away but the pair decided to continue in a second round with him.
Maundrell tripped Mr Hawkins and jumped on him and tried to punch him - but the fitter man blocked the blows before getting free.
Tara Wolfe, prosecuting, said: 'Mr Bennett made an effort to punch him again but the complainant punched back and Mr Bennett fell.
'Mr Maundrell got in the car and tried to start it. Mr Bennett went over to the car and was described as leaning all over it.
'In order to protect the car Mr. Hawkins punched Mr Bennett in the face again, causing him to fall to the floor.'
The cage fighter then dragged Maundrell out of his car and as he did so the thug shouted 'I’ve got a gun, I’ve got a gun,' to which Mr Hawkins replied 'Well get it out and shoot'.
Maundrell, 25, then said 'I’m going to blast you' but when the victim told him to give him his keys he threw them and fled.
Bennett hid behind some bins and Mr Hawkins told him to stay there until the police, who had been called by neighbours, arrived.
He was arrested soon after and found with a lock knife in his pocket.
Maundrell was caught a couple of months later when CCTV footage showed him close to the scene and he was picked out in an ID parade.
At the time, Maundrell was under a curfew for an earlier offence.
Jane Malcolm, for Maundrell, said he had been drinking heavily and could recall little of the incident.
She said: 'As a result of excess alcohol he has behaved like a drunken lout. At the time he was at a low place in his life.'
Will Woodman, for Bennett, said the men had been drinking all afternoon and had been thrown out of a nearby pub for being drunk before the incident.
Judge Euan Ambrose told the pair: 'These offences are so serious that in each of your cases only an immediate custodial sentence can be justified.'
Maundrell was jailed for 27 months and Bennett got 20 months.