Officers say Mark Andrew Nicol who's 29, has not been seen since 10.45 on the morning of Friday 12 October in the Bootham area of the city. They are asking for the public’s help to locate him.
He's described as white, 5ft 7in tall with a slim build and short brown hair. Police add that when Mark was last seen he was wearing a black jacket, black trousers and black shoes.
York police are growing concerned for Mark’s welfare as he has health issues and is not believed to have his essential medication with him.
They add that 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.