Early career Kelly started playing football with his local side in
Lucan,
Esker Celtic where he played from under 5's age group, right up to under 14's. He then played for
Lucan United from 2012 to 2014 before moving to
Peamount United where he caught the eye of
St Patrick's Athletic scouts.
St Patrick's Athletic Kelly signed for
St Patrick's Athletic on his 17th birthday ahead of their underage 2015 campaigns, with Kelly eligible for both the under 17 and under 19 sides. Kelly impressed for the under 19's among an excellent squad including
Fuad Sule,
Aidan Keena,
Darragh Markey,
Jamie Lennon,
Jonathan Lunney,
Rory Feely,
Conor Kane and Shane Elworthy, all of whom went on to play at senior level in the
League of Ireland Premier Division or abroad. His first involvement with the first team came on 16 October 2015, when manager
Liam Buckley included him on the bench for a league game with
Drogheda United, although he remained an unused substitute. Kelly and the under 19's were narrowly beaten by
Cork City in the final of the
Enda McGuill Cup on 13 September 2016. He made his first senior appearance on 25 October 2016 when he came off the bench for
Ian Bermingham in the 88th minute of a 5–2 win over champions
Dundalk at
Richmond Park. Unfortunately for Kelly and the Pats under 19's, on 1 November 2017, they again finished up their season up as runners up in the league, as they lost 1–0 in the final to
Bohemians at
Dalymount Park, in what was Kelly's last game in underage football. Kelly made 2 more appearances for the first team in the
2017 season, against Firhouse Clover and
Shelbourne in the
Leinster Senior Cup.
Drogheda United season With first team appearances at
St Patrick's Athletic limited, it was announced on 1 January 2018 that Kelly had been persuaded to sign for
Drogheda United by new manager
Tim Clancy. Kelly's first career goal came on 11 March 2018, in a 6–0 win over
Athlone Town at
United Park on the opening night of the season. He proved to be a mainstay in the team and a key player as Drogheda had a late push in the league to finish in 4th place ahead of
Longford Town to qualify for the
League of Ireland Promotion Playoffs. His side beat
Shelbourne over 2 legs before they were knocked out by
Finn Harps despite Kelly scoring a vital goal in the first leg to give Drogs the lead. Kelly's first full season in senior football saw him make 39 appearances in all competitions, scoring seven goals from his centre back position.
Return to St Patrick's Athletic On 20 November 2018, it was announced that Kelly had signed a contract back at
St Patrick's Athletic under new manager
Harry Kenny. Kelly's manager at Drogheda,
Tim Clancy stated soon after his move that he would not have left the club if it had been any club other than Pat's. Kelly's first league start came against
Finn Harps on 25 February 2019, with Kelly playing at left back, covering for the injured
Ian Bermingham. He had to wait until the 12 April away to
Cork City for his first start in his preferred centre back role and he impressed in a 1–1 draw which helped him nail down his spot in the starting 11 from there on. Kelly's first senior goal for Pats came in a 2–0 win over
UCD. His first appearances in Europe came on 11 and 18 July 2019 as he played in both legs against
IFK Norrköping of
Sweden, as Pats lost 2–0 at home and 2–1 away with Kelly being sent off in the 89th minute after 2 yellow cards. Kelly announced on his
Twitter account on 1 November 2019 that he was leaving
St Patrick's Athletic following the ending of his contract.
Bohemians Kelly was announced as a pre-season signing for
Phibsborough side
Bohemians before the 2020 League of Ireland campaign.
Ballymena United loan After just 3 appearances in all competitions for
Bohemians, Kelly was loaned out to
NIFL Premiership side
Ballymena United on the 1 October 2020 until January 2021. He made his debut in the opening game of the season, a 1–0 win away to
Coleraine at
The Showgrounds. Hiss first goal for the club came on the 19 December 2020 when he opened the scoring at home to
Glentoran in an eventual 1–1 draw. He returned to
Bohemians on the 11 January 2021 with his loan spell coming to a close.
Bradford City On 12 December 2022, it was announced that Kelly had signed for
EFL League Two side
Bradford City from 1 January 2023 on a two-and-a-half-year contract, until the summer of 2025. At the end of the 2024–25 season, Bradford City entered into discussions with him regarding a new contract. On 24 June 2025, the club announced that Kelly had signed a one-year contract extension. ==Career statistics==