Standard Liège On 22 August 2013, De Sart made his debut in the
UEFA Europa League against Belarusian
FC Minsk in a 2–0 away win. He played the full game. He's a youth exponent from the club. He is the son of
Jean-François De Sart who has been a board member of Standard Liège, and the elder brother of
Alexis De Sart who previously played for Standard Liège. He made his league debut at 25 August 2013 against
R.A.E.C. Mons in a 2–0 away win, coming off the bench in the first half for an injured
Yoni Buyens. After 83 minutes he was sent off with a second yellow card. At 24 November 2013, he scored the only goal against R.A.E.C. Mons.
Middlesbrough On 1 February 2016, it was confirmed that De Sart had joined English club
Middlesbrough of the
Championship side on a three-and-a-half-year contract for an undisclosed fee. On 5 January 2017, it was confirmed that De Sart would be moving to
Derby County on loan for the remainder of the season. He scored his first goal for Derby in a 4–3 loss to
Cardiff City on 14 February 2017. On 27 June 2017, De Sart was sent on loan to
Belgian Pro League team
Zulte Waregem for the
2017–18 season, thus making a return to Belgium after leaving
Standard Liège in January 2016.
Kortrijk In August 2018, De Sart left Middlesbrough and joined
Kortrijk.
Gent On 15 June 2021, he moved to
Gent on a three-year contract.
Al-Rayyan On 30 July 2024, Gent announced De Sart's transfer to
Al-Rayyan in Qatar. ==Career statistics==