Nigel Chambers, aged 46, was reported missing to police on May 24, after friends realised they had not seen him for more than a month.
Mr Chambers is from the St James/Dallington area of Northampton and is known to frequent those areas, as well as the Kingsthorpe area of the town. He also may have links to the Coventry area.
He is described as white, around 5ft 7in, of stocky build. His hair and beard are thought to be longer than in the photograph.
Officers are concerned for his welfare and are asking anyone with information about his whereabouts to contact Northamptonshire Police on 101.