Wakefield District CID would like to speak with anyone who can identify the man as enquiries continue into the incident which took place on Chantry Bridge behind the Hepworth Gallery on Sunday, March 10.
It took place between 1am and 1.10am after the 48-year-old victim was approached by a man who attempted to engage him in conversation.
Both males then assaulted him before making off with his bag.
The victim suffered a facial injury as a result of the assault and required hospital treatment.
Information can also be given online via West Yorkshire Police 101Livechat at https://www.westyorkshire.police.uk/101LiveChat or anonymously to the independent Crimestoppers charity on 0800 555 111.