He won a Jury Prize in Cannes Film Festival for Les Misérables in 2019.

He started making films with his friends Kim Chapiron, Romain Gavras, and JR, in the collective Kourtrajmé.

[2] He directed his first films, notably for Oxmo Puccino, and his first documentaries, 365 jours à Clichy-Montfermeil [fr] (365 days in Clichy-Montfermeil), filmed after the 2005 French riots; Go Fast Connexion; and 365 jours au Mali (365 days in Mali).

In the same year, he was nominated for the César Award for Best Documentary Film for À voix haute : La Force de la parole [fr] with Stéphane de Freitas [fr].

[7][8][9] In 2018 in Montfermeil, Ly created a free film school, called "L'école Kourtrajmé".