The force did not give any details about the nature of the investigation relating to events on May 21 this year.
Although six months have passed, they have been unable to identify the men or establish the full circumstances.
Today they released footage recorded on Clifford Street at about 4.15am on that day in the hope that a member of the public would recognise the pair.
A police spokesman said one of the two men was later pictured walking with a woman.
Anyone who recognises them is asked to call North Yorkshire Police on 101, select option 2 and ask for DC Vicki Hildred or York Serious Crime Team.
Alternatively, contact Crimestoppers anonymously on 0800 555 111.
Please quote reference number 12160088472 when passing information.