Craig Tilbury, 25, from Laurencekirk, Aberdeenshire, pleaded guilty to the culpable homicide of James Simpson in Public Street, Blairgowrie, on June 16 by punching him on the head and knocking him to the ground.
Advocate depute Bill McVicar, prosecuting, said that Mr Simpson, who lived with his partner and her two children in Coupar Angus, was in the Crown Bar, in Blairgowrie, and was asked to leave because he was intoxicated.
As he did so, service manager Mr Simpson made a lunge at Tilbury in a bid to punch or push him and struck him on the chest.
Mr McVivar said: "After this incident, the accused was clearly angry.
"He told his girlfriend he was going to the toilet, but instead went outside."
The High Court in Glasgow heard that Mr Simpson was at a taxi rank, when Tilbury hit him on the left side of the head.
Mr Simpson immediately fell and Tilbury walked away.
Shortly afterwards Tilbury handed himself in to the police and admitted what he had done.
Mr Simpson, who suffered bleeding to the brain, was taken to Ninewells hospital in Dundee, where he was pronounced dead at 12.08am on June 17.
Mr McVicar said: "The brain injury was inevitably fatal and caused by a single punch."
Defence QC Donald Finlay said: "Mr Tilbury has a profound degree of remorse."
Judge Norman Ritchie QC deferred sentence but told Tilbury: "It is almost inevitable a custodial sentence will be imposed."