Marceau was born Sophie Danièle Sylvie Maupu in Paris, France, the second child of Simone (née Morisset), a clerk, and Benedict Maupu, a truck driver. The family lived a life of the working class, who left Marceau with generally good memories of childhood. During the week she helped the family restaurant. She spent the weekend with her family in the cabin, a small house in Vert-le-Petit in the Essonne department. Her parents divorced when she was nine.
In February 1980, Marceau and her mother was a modeling agency looking for teenagers. Marceau had photos taken at the office, but did not think anything would come of it. At the same time, Françoise Menidrey, the casting director for Claude Pinoteau in La Boum (1980), asked modeling agencies for a new guy to recommend for the project. After viewing the rushes, Alain Poire, the director of the film company Gaumont, Marceau signed a long-term contract. The Tree was a success not only in France, where 4.5 million tickets were sold, but some other European countries and Japan.
In 1981, Marceau began her career singing with French singer François Valéry on "Dream in Blue", written by Bertrand Delanoë.