Greatham, County Durham born centre half Harry Thoms began his football career with Greatham in 1914 but after the First World War he joined North Eastern League club Hartlepools United in December 1919. When they joined the newly formed Third Division (North) in 1921 Thoms made his Football League debut in their inaugural League fixture at Wrexham the same August, and scored once in 34 appearances that season before joining Second Division club Derby County in the summer of 1922, who took him along with manager Cecil Potter and team mate Tommy Crilly.
He played in Derby’s 1923 FA Cup semi final, when they lost 5-2 to West Ham United at Stamford Bridge, and became club captain, leading The Rams to promotion in 1926 as Second Division runners up. He was then an ever present in their first season back in the top flight, before losing his place in November 1928, after which he joined Crystal Palace in the summer of 1929 in a joint deal with Tommy Crilly having scored 4 goals in 195 appearances for The Rams. He had one season at Selhurst Park scoring once in 7 appearances, before a transfer to Irish League Glentoran in 1929, his final club before his eventual retirement.