Humberside Police say the 21-year-old victim had been involved in a verbal altercation with three men known to him, during a night out in The Vault, Bethlehem Street, on Friday, November 11.
He left the bar in the early hours of November 12 and was walking towards West St Mary’s Gate, when he was assaulted.
He was left unconscious and found by a member of the public, who called an ambulance. He was then taken for treatment at Diana, Princess of Wales Hospital and later discharged.
Anyone with information is asked to call 101, quoting crime reference number 2230218.