In 2015, De Mil received an offer from Club Brugge to become a youth coach, following the departure of Sven Vermant.
On 18 February 2021, he replaced Philippe Clement as head coach of Club Brugge in the Europa League round of 32 match against Dynamo Kyiv which ended in a 1–1 draw, during the COVID-19 pandemic.
[3] Ahead of the 2022–23 season, Club Brugge announced that De Mil would be promoted to the first team, where he became assistant to Carl Hoefkens.
[7] He achieved better results, which saved the club from relegation, but was still dismissed on 19 March 2024, following the controversial 1–1 draw in the last match of the regular competition against Genk.
[8] On 22 March 2024, Sporting Charleroi announced the signing of a 2-year contract with De Mil, replacing Felice Mazzu.