Geoff Sidebottom was born in Mapplewell, Yorkshire in 1936. He joined Wolverhampton Wanderers from their Yorkshire-based nursery club Wath Wanderers in 1954. Due to the talent of Bert Williams and Malcolm Finlayson, he had to wait until 1 November 1958 to make his first team debut, in a 2–1 defeat to West Bromwich Albion.
He managed 35 appearances for Wolves, including playing in the 1960 Charity Shield, before moving to Aston Villa in February 1961. He broke through to their starting XI and played in their 1962 League Cup triumph.
After 88 games in total for Villa, he joined Scunthorpe United in January 1965 and was a near-ever present in the 1965-66 season for them before losing his spot to the emerging Ray Clemence.
He had a spell playing in America with the New York Generals during 1967-68 when signed by his former Scunthorpe manager Freddie Goodwin. He later followed Goodwin back to England to join Brighton & Hove Albion in January 1969 before retiring in 1971. Geoff played 45 matches for the Seagulls.