She decided to become an actress during her youth, after having admired actresses in films. She then took acting lessons in Lyon with the actor and director Christian Taponard. In 1989, she moved to Paris to study history, as well as drama lessons in free classes at Cours Florent, then at the National Conservatory of Dramatic Art for three years, with Jacques Lassalle and Catherine Hiegel for teachers.
In the early 1990s, she obtained her first small roles in the cinema, then in feature films such as The Story of the Boy Who Wanted to Be Kissed by Philippe Harel (1994), Le Plus Bel Age..., by Didier Haudepin (1995) or even Love, etc. by Marion Vernoux (1996).
In 1997, Sylvie Testud experienced her first great success at the cinema in Germany with the film Beyond Silence by Caroline Link, for which she learned German, the clarinet and sign language. She is rewarded as best actress by the German Film Prize (the equivalent of the C茅sar for best actress). In 1998, she played her first major role in French cinema and enjoyed great success in France with the role of B茅a in Karnaval, the first feature film by Thomas Vincent, for which she was nominated for the C茅sar for best female hope and received the Michael Simon Prize. She then began an important acting career with a preference for auteur cinema.
In 2000, her performance in La Captive by Chantal Akerman (adaptation of the novel La Prisonni猫re by Marcel Proust) earned her a nomination as best actress at the European Film Prize. In 2001, she obtained, for her second nomination, the C茅sar for best female hope for the remarkable interpretation of Christine Papin, one of the Papin sisters, in Les Blessures assassines by Jean-Pierre Denis, based on a news item from 1933.