Ledoyen was born in Paris and raised in Aubervilliers, the daughter of Olga, a restaurateur, and Bernard Fernández, a merchant who sold cleaning products and knives.

Ledoyen's film breakthrough came with A Single Girl (1995) (stylized la fille seule), for which she was nominated for a César Award for Most Promising Actress.

She also received two César Award nominations for Les marmottes (1993) and L'eau froide (1994).

She portrayed the character Cosette in the 2000 French television miniseries of Les Misérables.

On 29 September 2001, Ledoyen gave birth to her first child, a girl named Lila, with production designer Louis Soubrier, whom she met on the set of La fille seule in 1995.