On 24 January 2019, Niasse signed a professional contract with Lille OSC for three years.[1] Niasse made his professional debut for Lille in a 3–0 Ligue 1 win over AS Saint-Étienne on 28 August 2019.[2]
On 10 December 2020, he made his debut in the UEFA Europa League in a group match against Celtic.
On 1 February 2021, Niasse moved to Greek club Panathinaikos, on a loan deal until the end of the season.[3]
On 3 February 2022, Niasse signed a contract with Young Boys in Switzerland until June 2026.[4]