Mark Andrew Nicol, 29, has not been seen since 10.45am on Friday 12 October 2012, in the Bootham area of the city.
He is white, 5ft 7in tall with a slim build and short brown hair. When Mark was last seen he was wearing a black jacket, black trousers and black shoes.
Police are growing concerned for Mark’s welfare as he health issues and is not believed to have his essential medication with him.
Although It is not known where Mark is, he does have links to Sunderland, Tyne and Weir.
PC Elaine Duffy, of Clifton Moor Safer Neighbourhood Team, said:
Mark, if you see or hear this appeal please get in touch with the police straight away, so that we can confirm you are safe and well.
If you have seen Mark since Friday 12 October 2012, or know where he is please contact North Yorkshire Police as soon as possible.
Anyone who can help locate Mark Nicol is asked to contact North Yorkshire Police on 101, select option 1 and pass the information to the Force Control Room.