Police are investigating an assault at a licensed premises in the CBD on October 26.
Investigators have been told an unknown man assaulted the victim on level two of the Bourke St club at about 3am.
The 40-year-old man was treated for non-life threatening facial injuries.
The offender left with a group of people and was last seen walking on Flinders St.
He is described as 170cm tall, medium build, short cropped black hair and was wearing a red checked shirt.
Police have released images of a man they believe may be able to help them (above).
Please contact Crime Stoppers on 1800 333 000 or submit a confidential crime report at www.crimestoppersvic.com.au