Fletcher, and his twin brother Tyler, spent nine years as part of the academy at
Manchester City prior to signing for
Manchester United for a combined fee of £1.25 million in July 2023. In November 2023, Fletcher was invited to train with the Manchester United first-team squad. He signed his first professional contract with the club in April 2024, shortly after his 17th birthday. In August 2024, Fletcher scored twice, including a long-range volley in a 3–2
EFL Trophy victory against
Barnsley for the Manchester United under-21 side. He was named in a first-team matchday squad for the first time on 19 October 2024, for a
Premier League match against
Brentford. On 21 December 2025, Fletcher made his debut for Manchester United as a 76th-minute substitute in a 2–1 loss to
Aston Villa in the Premier League. With his brother Tyler also making his debut for the club that season, it marked the first time that two twins and their father had all played in the English top flight. On 4 March 2026, Fletcher was given a six-match suspension and fined £1,500 for calling an opponent a "gay boy" while playing in
Manchester United U21's 5-2 loss against Barnsley's first team in the EFL Trophy the previous 21 October. ==International career==