Sy began his career after high school in 1996, working at Radio Nova, where he met his comedy partner Fred Testot. Afterwards, he appeared in the TV show Le Cinéma de Jamel on Canal+, with Jamel Debbouze. He then created a TV show called Le Visiophon. Following these roles, he appeared in various TV and stage shows such as Je ne fais pas mon âge and Omar et Fred: le spectacle. Most notably, Sy co-hosted Service après-vente des émissions, a French short comedy television series, with Testot from 2005 to 2012 on Canal+ until it was cancelled.
