Hartigan joined AFC Wimbledon aged 14, after being spotted playing for the coaching company Pro Direct Soccer. He signed his first professional contract on his 17th birthday.[3] On 8 August 2017, he made his debut in a 3–1 EFL Cup defeat to Brentford.[4] Playing the full 120 minutes, with the game going to extra time, he became the first player to represent AFC Wimbledon born in the 2000s.[5] He scored his first goal for Wimbledon in an EFL Trophy tie against Barnet on 29 August 2017.[6]
On 15 April 2018, Hartigan was named the LFE Apprentice of the Year award for League One at the EFL Awards ceremony in London.[7]
Following relegation, Hartigan was offered a new contract at the end of the 2021–22 season.[8] On 5 July 2022, AFC Wimbledon announced that Hartigan had decided to leave the club following the expiry of his contract.[9]
Newport County (loan)
Hartigan joined League Two club Newport County on loan until the end of the 2020–21 season on 25 January 2021.[10] He made his debut for Newport in the starting line up for the 2–1 defeat against Harrogate Town in League Two on 30 January 2021.[11] Hartigan played for Newport in the League Two play-off final at Wembley Stadium on 31 May 2021 which Newport lost to Morecambe, 1–0 after a 107th minute penalty.[12]
Mansfield Town
On 4 August 2022, Hartigan signed for League Two club Mansfield Town on a two-year contract, a compensation package being agreed with AFC Wimbledon on account of Hartigan's age.[13] Hartigan played frequently early in the season, but was sidelined after a shoulder injury on New Year's Day.[14]
Barnet (loan)
In August 2023, Hartigan joined Barnet on a season-long loan.[15] For the 2023–24 season, Hartigan was named as Barnet's Players' Player, Manager's Player and Young Player of the Season for the campaign.[16] He also received the club's Goal of the Season award.[16]
On 7 May 2024, Mansfield announced he would be released in the summer when his contract expired.[17]
Barnet
On 24 June 2024, it was announced that Hartigan had joined Barnet on a permanent basis on a two-year contract.[18]
Personal life
Hartigan is of Welsh descent through his great-grandmother.[19]