Staff and regulars were horrified when the punter decapitated the terrified bird in the busy bar.
It was due to be adopted by a local bird lover before the customer got his hands on the harmless pigeon.
Blood spurted across the bar and managers had to shut the pub while it was deep cleaned.
Police have been called in to investigate and are viewing CCTV of the horrific beheading at the Pipeworks pub in Pontyclun, Mid Glamorgan, Wales.
Barman Sam Cooper said: "He was a lovely pigeon, he'd sit on a chair next to customers.
"He was really tame and we found someone to take him in as a pet.
"But the day before he was due to go the man came in and asked if we wanted to get rid of him.
"We sort of guessed what he meant and went: "No, no no."
But the man in his fifties grabbed hold of the pigeon and snapped its head off in front of shocked customers.
He ran out and leaving a mass of blood and feathers on the pub floor.
Mr Cooper said: "It was horrible - we had to shut the next day for the pub to be deep cleaned.
"The fellow came back in a couple of days later but the manager refused to serve him."
Locals rang the police to report the act of animal cruelty and the pub handed over its CCTV when cops arrived.
A regular said: "It was a disgraceful thing to do to a harmless creature.
"Customers were fond of the pigeon, they would feed it bits of bread and crisps.
"Its wings were still flapping after its head was torn off. I hope the police prosecute the bloke who did it."
A South Wales Police spokesman said: "We received a report of animal cruelty in Pontyclun. The matter is being investigated."