Middlesbrough Hackney joined
Middlesbrough's academy after being spotted playing for his local side
Redcar Town. Having been part of the Middlesbrough team that reached the under-18 Premier League Cup final in 2019, he signed his first professional contract with the club on 26 June 2019, his 17th birthday. Shortly after being named on the first-team bench for a match against
Barnsley in November 2019, he was praised by Middlesbrough manager
Jonathan Woodgate, with Woodgate claiming "Hayden Hackney deserves to be there because he's been outstanding for the Under-23s". He made his league debut for the club in the final match of the season as a substitute in a 3–0 defeat to
Wycombe Wanderers. He signed a new two-year contract with the club later that month. On 31 August 2021, Hackney joined
EFL League Two side
Scunthorpe United on loan until January 2022. After playing in the majority of games in the first half of the season, Hackney's loan was extended to last until the end of the season. In the 15th minute of a 2–0 defeat to
Exeter City, Hackney was caught spitting at an opponent. The referee did not see this at the time, but after the game,
The Football Association confirmed that Hackney had admitted to spitting and was given a six-game suspension. He made 31 appearances as Scunthorpe were relegated to the
National League. Hackney's game time at Middlesbrough was limited at the start of the
2022–23 season, but Hackney became a regular starter following the appointment of
Michael Carrick as manager in October 2022. On 19 October, Hackney scored his first goal for
Middlesbrough in a 4–1 win against
Wigan Athletic. On 8 December, he signed a contract extension until 2026. but lost out to
Bristol City's
Alex Scott. On 28 June 2023, Hackney signed a new contract for Middlesbrough, keeping him to the club until the summer of 2027. Hackney captained the club for the first time in a 1–0 home defeat to
Aston Villa in the
FA Cup on 6 January 2024. On 9 January, he scored the only goal in a 1–0 victory over
Chelsea in the first leg of the
EFL Cup semi-final. ==International career==