Debbouze is the oldest of five brothers. He was born in Paris, France, but his family moved to Morocco the following year. They returned in 1979 and settled in Trappes, where Jamel spent the rest of his childhood.
On 17 January 1990, at the train station in Trappes, he was struck by a passing train travelling at 150 km/h. He lost the use of his right arm, while another young man, Jean-Paul Admette, died. After this accident Debbouze met Alain Degois, his mentor, and began his career as a comedian/actor.