Police said Mohammed Faisal, 32, was assaulted just before midnight on November 11 outside McFly's bar in Commercial Street.
He was treated by paramedics at the scene before being taken to Leeds General Infirmary.
But West Yorkshire Police today said they have now launched a murder enquiry, after Mr Faisal died on December 4.
It comes as Mr Faisal's family today also released the first photo of him.
A 30-year-old man, who was arrested previously on suspicion of assault, has since been arrested on suspicion of murder.
Police said he has been released not bailed pending further enquiries.
The force is appealing for any witnesses to come forward.
Detective Chief Inspector Glen Alderson, of West Yorkshire Police's Protective Services (Crime) Department, said: “I want to appeal to anyone who witnessed this incident to come forward. We have previously released CCTV images of people we wanted to trace in connection with this and have traced all of those people.
“I still want to speak to anyone who may have witnessed what happened but who hasn’t yet come forward with information. Mr Faisal’s family have released a photo of him.”
Anyone with information is asked to call police on 101, quoting crime reference 13170528002.