Stephen Briggs, 31, had drunk 16 cans of lager when one of his children disturbed him in his garden shed.
He lost his temper and started throwing whatever came to hand – including one of his children's pet guinea pigs.
The poor animal didn't die straight away and when police arrived one of the kids - who are aged seven, 10 and 11 - was trying to comfort it before it moved, then died.
At Carlisle magistrates' court, Briggs pleaded guilty to causing a protected animal unnecessary suffering and to criminal damage.
In court, Briggs, now living at Guisborough, Cleveland, blamed his actions on his drinking, saying: "I was in the wrong."
He said he was now living with his parents and worried that his children might think he was evil.
He added that he hopes to go back to his wife and family.
The case was adjourned for reports and Briggs will be sentenced on Monday, August 13.