Keillor-Dunn spent his youth career at Middlesbrough, Sunderland and Chesterfield[3] before moving to Ross County on 22 July 2016. Whilst playing for the youth team in the 2016–17 season, he was one of the stand-out performers as they won their first Development League title. He was awarded a first team contract in summer 2017.[3]
On 9 August 2017, he made his senior debut coming on as a substitute against Motherwell in the League Cup.[4] On 9 September 2017, he made his first competitive start in the League against Partick Thistle, impressing in a 1–1 draw.[5] On 14 October 2017, he scored his first goal for the club in the League against Hearts.[6] He signed a new contract on 31 October 2017 after his initial break-through into the first team.[7]
Keillor-Dunn moved on loan to Falkirk in January 2019.[8] His first goal for Falkirk was against Queen of the South, where he was also sent off in the match.[9] He left County by mutual consent in September 2019, after requesting more game time.[10]
Wrexham
On 16 January 2020, Keillor-Dunn signed for Wrexham until the end of the 2019–20 season.[11]
After scoring five goals in four consecutive matches as Oldham fought against relegation, Keillor-Dunn was awarded the EFL League Two Player of the Month award for February 2022.[14] Following Oldham's relegation to the National League, Keillor-Dunn was released by the club at the end of the 2021–22 season.[15]
Burton Albion
On 28 June 2022, League One club Burton Albion announced the agreement of a two-year deal with Keillor-Dunn.[16] He scored six times in 26 appearances for Burton,[17] including a first career hat-trick in a 4-4 draw at Accrington Stanley on 13 August 2022.[18]