Marie-Belle Sandis studied in Paris and Lyon. Her first engagement took her to the Opéra de Lyon as a member of the ensemble.

This was followed by engagements in Toulouse and at the Théâtre Royal de la Monnaie in Brussels (title role in Ravel’s L’Enfant et les sortilèges). In 2002–03 she was engaged in Gelsenkirchen, where she sang Béatrice in Béatrice et Bénédict and Ramiro in La finta giardiniera.

She has been a member of the National Theatre ensemble since 2003–04 and made her debut as as Dorabella, Donna Elvira, Vitellia, Cecilio, Annio, Silvia, Octavian, the Composer, Hansel, Charlotte in “Werther”, Giulietta in The Tales of Hoffmann, the Actress in La Voix humaine, Rosina, Adalgisa, Giovanna Seymour in Anna Bolena, Elisabetta Maria Stuarda, Sara in Roberto Devereux, Laura in La Gioconda and Suzuki.

Guest engagements have taken her to the Ruhrtriennale (Die Zauberflöte, Jeanne au Bûcher by Honegger), the Salzburg Festival with Ascanio in Alba, the Semperoper Dresden in La clemenza di Tito, the Aalto-Theater Essen in Don Giovanni, Madama Butterfly, The Tales of Hoffmann, Orpheus in the Underworld), to the Stuttgart State Opera in Lucio Silla and Die Zauberflöte, to the Hanover State Theatre, to the Giessen Municipal Theatre in the title role of La Cenerentola and to the Opéra Royal de Wallonie in Liège in Les Huguenots by Meyerbeer.

She has sung under the direction of Stuart Bedford, Dan Ettinger, Ádám Fischer, Louis Langrée, Marc Minkowski, Kent Nagano, Michel Plasson, Alexander Soddy, Stefan Soltesz and Marcello Viotti.

A DVD with her as Silvia in Ascanio in Alba was released in 2006.