[3] His first major role came in 1999, in Jacques Maillot's film Our Happy Lives.

The following year, he appeared in another Cantet film, Human Resources, which earned him a César Award for Most Promising Actor in 2001.

[4]Lespert's career took off and he appeared in several films, playing a wide range of characters, such as a sensual gardener in Sade,[5] a body builder addict in Vivre me tue,[1] a boxer in Virgil,[6] a pretentious artist in Alain Resnais's Not on the Lips,[7] and a journalist in Robert Guédiguian's The Last Mitterrand.

[8] Lespert directed his first film in 2007, 24 mesures, featuring Benoît Magimel and Sami Bouajila.

[10] In 2010, he appeared in the French television series Pigalle, la nuit.