Christopher Mulligan, 26, was last seen on Thursday, May 25.
Police now say they are concerned for the welfare of Mr Mulligan, who is thought to possibly be in the Rochdale or Burnley areas.
Detective Inspector Craig Lord of Calderdale CID, said: “Christopher has not been seen Thursday and his family and friends are understandably very worried about him.
“I would appeal directly to Christopher, or anyone who sees him to get in contact immediately.”
He is described as white, 5ft 6ins tall, with short mousy brown hair and a short brown beard.
Anyone with information is asked to call police on 101, quoting log 702 of Thursday May 25.