The Sunderland-born attacker signed for Middlesborough as a youngster before switching his football education to his home town club and latterly Chesterfield.
In 2016 he moved north of the border joining Ross County winning the Development League title as one of the stand-out performers in the division. As reward for his performances he signed his first professional contract with the Staggies in 2017.
Keillor-Dunn made his professional debut in August 2017 as a substitute against Motherwell in the Scottish League Cup, and scored his goal in October of that year against Hearts in the Scottish Premiership. He impressed in the opening months of his Ross County career and signed an extended deal later on in October 2017.
In 2019 Keillor-Dunn requested more game time and was loaned to Scottish Championship side Falkirk scoring five goals in eleven appearances, including a goal in their derby with Dunfermline.
The Wearsider left County in September 2019 to seek more game time and spent time with a number of clubs before being snapped up by Wrexham.
He made his Dragons debut coming off the bench in a 3-0 National League win over Woking.