A customer suffered bruising to his legs and chest in an assault at the Woodbourne pub in Douglas.
Michael William Steven Hanger, aged 30, of Victoria Street, Douglas, admitted punching his victim several times in the ribs.
He pleaded guilty to charges of assault causing actual bodily harm and affray and will be sentenced on September 3 after a probation report has been prepared.
Prosecutor Hazel Carroon told the court how police were called to the Woodbourne in Douglas at 8pm on Sunday (July 14).
Two men said they had been sat in the corner of the pub when there had been some banter about a seat which a regular sat in.
One of the men went to the bar and said he suddenly felt pain in his ribs as he was punched by Hanger several times.
Another man separated the two men and CCTV footage captured the incident.
A doctor examined the complainant and found that he had bruising to his leg and chest as well as a 2cm wound above his eye.
When interviewed, Hanger told police he had been defending his friends but admitted punching the victim two or three times.
He said he had felt threatened but when shown the CCTV admitted he had over-reacted. He said that the eye injury had been caused by the victim falling over.
Defence advocate Matthew Wilshaw asked for the probation report to be compiled and said that his client had been put on gardening leave by his employer.
High Bailiff Jayne Hughes ordered that the report consider all options, including custody.
Bail continues.