It took place at around 5.40pm on Thursday 13 February 2014, on the decking outside the Vodka Revolution Bar, Coney Street.
As a result of the assault the victim, a 59-year-old man from York, suffered a serious injury to his face which needed treatment at York District Hospital.
It is thought that the man officers need to trace, may have been visiting the city with a group of friends from Sunderland.
PC Damion Liversidge, of York Safer Neighbourhood Team, said: This was a nasty incident which left the victim needing medical treatment. I ask anyone who witnessed the assault or can help to identify the suspect to get in touch as soon as possible.
If you are the man caught on camera and you are not responsible for this assault, I urge you to contact me straight away so that I can eliminate you from my enquiries.
Anyone who can help officers progress this investigation should contact York police on 101, select option 2 and ask for Damion Liversidge. Alternatively, information can be emailed to email@example.com
Or call Crimestoppers anonymously on 0800 5551111, quoting reference number 12140025732.