The 67-year-old was last seen on Croft-an-Righ in Inverkeithing around 7pm on Wednesday, November 24.
The missing man is described as around 6ft in height, of stocky build, with grey/white short hair and brown eyes. He speaks with a Canadian accent.
Police Scotland has said there is no description of his clothing.
Sergeant Edmund Coxon said: “We are becoming increasingly concerned for Gavin’s welfare and are keen to find him as soon as possible.
“We would appeal to anyone with information on his whereabouts or anyone who has seen anyone matching his description to get in touch.”
Anyone with any information is asked to contact 101 quoting incident 2036 of November 24, 2021.