Nicholas Farnell, 32, lost his temper in an argument with Willy Pottage, 56, and his wife after they went out leaving their puppy barking in their garden, Winchester Crown Court was told.
Michael Sayers QC, for the prosecution, said the Pottages, of Elgar Walk, Waterlooville, Hampshire, had bought the dog a few weeks earlier.
"In the week or so before the incident, when they were out, the puppy would be left in the garden. Whilst in the garden, the puppy used to bark a lot and this barking apparently upset the defendant."
On 6 May, the Pottages went shopping, again leaving the puppy in their garden. As they returned to Elgar Walk, Mr Farnell, a roofer, complained about the noise, the court was told.
Although Mr Pottage apologised and said that the dog would grow out of it, Farnell continued his complaint. He accused the couple of cruelty to the animal and threatened to report them to the RSPCA.
Becoming irritated, Mr Pottage swore at Farnell and told him to go away.
Farnell, who denies murder but admits a charge of manslaughter, went to his car and returned with a crowbar, saying: "You want some, do you?"
The jury was told that he hit Mr Pottage on the head. As Mr Pottage fell, he banged his head on the road.
When his aghast wife said "Look what you have done", Farnell replied "Do you want some?"
Mr Pottage died in hospital four days later. His right jaw and the back of his skull had been fractured. Farnell told police who were called to the scene: "We are neighbours and it was all over a dog.
"We had a huge argument. I was already uptight and I just flipped and hit him over the head."
He later said he had not intended to cause Mr Pottage any harm, saying he had felt intimidated by the Pottages, who were both about 6ft tall.
Mr Sayers said the defence would argue that Farnell had not intended really serious harm and put forward a case for diminished responsibility.
The trial continues today.Reuse content