Talawa Holmes, 27, was last seen at the library in Todmorden yesterday (Octoer 12) shortly after noon.
He is described as white, with long, dark brown hair, blue eyes and stubble.
He has a tattoo on his right arm and he was last seen wearing black shoes, trousers and a black jacket.
A spokesperson for West Yorkshire Police said: "Police and his family are very concerned for his welfare.
"Anyone who has seen Talawa or who knows where he is, is asked to contact police on 101 or contact us options on the police website www.westyorkshire.police.uk quoting log 768 of 12 October."