Gainsbourg is the daughter of French singer, songwriter and actor Serge Gainsbourg and the British actress Jane Birkin. She grew up in the public eye not only because she had celebrity parents, but because she had celebrity parents who had never married, lived openly together and had a child. (They separated when Charlotte was nine years old.) She made her screen debut in 1983 as Catherine Deneuve's daughter in "Love Songs", a film about divorce. Two years later, director Claude Miller cast Gainsbourg as the tempest-tossed adolescent in "L'Effrontee", and before she was 15, Gainsbourg had won a Cesar, the French counterpart of the Oscar, for her performance. In 1989, American audience saw Gainsbourg for the first time in "The Little Thief", this time as a precocious teen. She has since appeared in several other films, including the British "The Cement Garden" (1993), directed by her uncle Andrew Birkin, and "Kung Fu Master!" (1987), written by and starring her mother. Gainsbourg also starred in the Paris production of David Mamet's "Oleanna" (1995).

The actress would continue to appear in several European films and television productions, the most accaimed of which was her real-life husband writer-actor-director Yvan Attal's boisterous and enjoyable French romantic seriocomedy "Ma Femme Est une Actrice" (2001), known to American audiences as "My Wife Is an Actress." Gainsbourg played the highly desirable actress-wife of a jealous Parisian sportswriter who frets over the multiple opportunities to stray that may or may not be presented to her by her handsome, older co-star (Terrence Stamp). The film won praise in many critical circles and spotlighted Gainsbourg's beguiling mix of willowy plaintiveness and slightly irregular beauty. In 2003 Gainsbourg returned to an American film and received strong notices for her performance in "21 Grams" as Mary, the previously estranged wife of a dying math professor (Sean Penn) who is determined to get pregnant with his child through artificial insemination when a heart transplant revives him but not their love.