James Wodrow, 72, was last seen at his home address on August 21 at around 11am. He is described as white, medium build, about 5ft 5in tall with grey receding hair and a Scottish accent. He was last seen wearing glasses, a grey or brown fleece jacket and a cream coloured cap.
It is believed that Mr Wodrow could be in Edinburgh or the Northumbria area.
A police spokesman said: “We would ask that James makes contact with the police or his family as soon as possible.
“There are concerns for his safety and welfare at this time. Anyone with information about James’s whereabouts should call Hertfordshire Constabulary on 0845 3300222.”