West Bromwich Albion On 3 July 2019, Harmon signed his first professional contract with
West Bromwich Albion, penning a two-year deal. On 27 May 2021, the club announced he would leave the club following the expiration of his contract.
Oxford City On 6 August 2021, following his release from
West Bromwich Albion earlier that summer, Harmon signed for
National League South side
Oxford City following a trial with the club. Harmon made 43 appearances for the club, scoring seven goals, and won the Supporters' Player of the Season award.
Ross County On 22 June 2022, Harmon signed a two-year contract with
Ross County. On 19 July 2022, Harmon made his first start for the club after he replaced
Ben Purrington in Ross County's 2–0 victory against
Alloa Athletic in the
Scottish League Cup. On 6 August 2022, Harmon made his first appearance in the Scottish Premiership in a 3–1 defeat to Celtic after he replace Jordy Hiwula. He scored his first goal for the club on 5 November 2022, in a 3–2 win against
St Mirren. On 17 June 2024, he signed a new two-year contract with the club.
Cheltenham Town On 8 August 2025, Harmon returned to England, joining
League Two club
Cheltenham Town on a one-year deal. He made his debut for the club on 9 August 2025, in a 2–0 defeat to
Chesterfield. ==Career statistics==