Robert Fletcher aged 60 was last seen on September 8 in the Saltford area and he has not been in contact with friends or family since.
Police believe he may be in the Bristol area and are growing concerned for his safety and welfare.
Mr Fletcher is around 5ft 11 inches tall and of a slim build. He has grey hair and speaks with a Scottish accent.
If you see Mr Fletcher contact the police on 0845 456 7000.