[7] Soon after his appointment as Celtic head coach, Brendan Rodgers invited Dembélé to participate in a light technical training session with the first-team squad.

[10][11][12][13][14][15] He was named on the bench because several regular starters were away playing for Scotland's under-19 team and was brought on during the 81st minute, replacing the youngest first-team player in Celtic's history, 16-year-old Jack Aitchison.

[16] A match report on the official Celtic website stated that "the diminutive playmaker didn't look out of place and played his part in the closing stages.

"[17] The response to Dembélé's under-20s debut included concern about the physical and mental impact of such a young player being fast-tracked through the developmental ranks.

After the match, Dembélé collected his winners' medal and helped to lift the Scottish Premiership trophy as Celtic ended the season nine points clear at the top of the league.

[28] In October 2019, L'Équipe named Dembélé as one of six "outstanding young players set to revolutionise the game", a list that also included Barcelona's Ansu Fati.

[29] On 12 December 2019, Dembélé became the youngest-ever footballer to play for a Scottish team in European competition when he came on as a substitute in Celtic's 2–0 loss away against Romanian side CFR Cluj.

[33] He sustained a fractured ankle during a pre-season friendly against Bristol City in July 2021, and eventually had to undergo an operation in October 2021.

[34][35] He made his return to action on 13 February 2022, playing in Celtic B's 4–0 win over Vale of Leithen in a Lowland Football League fixture.

On 13 August 2024, Dembélé returned to England, joining Championship club Queens Park Rangers on a season-long loan.

[48] On 30 September, Queens Park Rangers announced that Dembélé will join the English club permanently, effective from the summer of 2025.

[54] Prior to participating in the Victory Shield, Dembélé travelled south in October 2016 to train with England under-15s at St George's Park.