He played as a wing half. He began his football career as an apprentice with Birmingham City in 1961, and turned professional the following year. Described as a "tall, well-built midfielder with a powerful shot", Farmer scored on his debut in the First Division on 1 February 1964, deputising for Malcolm Beard in a 3–2 defeat at Ipswich Town.
This proved to be his only first-team appearance for the club, and in the 1965 close season he joined Lincoln City.
Farmer spent only one season with Lincoln, playing 22 games, all in the Fourth Division, before moving into non-league football with Skegness Town and Arnold Town. Prior to the 1970-1971 season he signed for Grantham, then playing in the Midland League.
After leaving professional football he worked in finance.
By the time his Grantham career ended some four-and-a-half years and 143 games later, he had won two Midland League titles, a Southern League Division One North title and contributed to the club"s Southern League runners-up spot in 1974, though in 1973-1974 season he spent time on loan at Oadby Town and took no part in Grantham"s run to the Third Round of the FA Cup.