Police responded at about 10:30 a.m. PT to the report of an assault and found one man suffering from serious injuries. The man was rushed to hospital where he was later declared dead, police spokesman Sgt. Randy Fincham said.
Witnesses said paramedics at the scene were administering chest compressions, an indication the victim's heart had stopped beating.
The deceased, whose identity has not been made public, was a longtime member and volunteer at the Kettle Friendship Society, on Venables Street, locals have told CBC News.
Fincham said investigators from the Vancouver Police Major Crime Section and the Forensic Identification Unit will be at the scene throughout the day.
Police said one other man was involved in the fight, and late Saturday afternoon they announced the arrest. Police have not said whether the man is a suspect or a person of interest. No charges have been laid.
It is Vancouver's second homicide of 2013.