At the age of 9, Marion Tassou entered the children's choir of the Nantes Opera. She then studied singing at the Conservatoire National de Région de Nantes and at the Conservatoire National Supérieur de Musique et de Danse von Lyon. In 2008, she sucessfully obtained her Master's Degree. At the same time, she took private lessons with Donatienne Michel-Dansac, Cécile de Boever and Alain Garichot. She also attended masterclasses with François Leroux and Udo Reineman. In 2015 she was awarded, together with pianist Yannaël Quenel, the Prize of the contemporary song at the "Concours international d'interprétation de la mélodie française" in Toulouse.
Marion Tassou is open to all repertoires from baroque to today's music. She has performed Vénus in Le Carnaval et la Folie by Destouches, Euridice (Orfeo ed Euridice) in Limoges, Ilia (Idomeneo) and Pauline (La vie Parisienne) in Montpellier, Pamina (Die Zauberflöte) and Zerlina (Don Giovanni) at the Festival de Saint Céré, Blanche de La Force (Dialogues des Carmélites) with the Atelier Lyrique des Pays de Savoie. After being a member of the Académie of the Opéra Comique in 2013/14, she took part in three world premieres: L'Autre hiver by Dominique Pauwels with LOD Muziektheater in the frame of "Mons, European Capital of Culture", Beach Bosch by Vasco Mendonça again with LOD Muziektheater for the 500th Anniversary of the death of the painter Hieronymous Bosch and Le Mystère de l'écureuil bleu by Marc-Olivier Dupin at the Opéra Comique. She also performed Hahn's L'île du rêve (Mahenu) at the Théâtre de l'Athénée in Paris, Mozart's Le Nozze di Figaro (Contessa) touring with the company Opéra éclaté, Monteverdi's Il ritorno d'Ulisse in Patria (Melanto) at the Staatsoper Hamburg and Schönberg's Pierrot Lunaire on tour with the ensemble La Belle Saison.
In concert, Marion Tassou has recently sung Fauré's Requiem with the Gürzenich Orchester under the baton of François-Xavier Roth, Béatrice et Bénédict (Héro) with Les Siècles and François-Xavier Roth at the Berlioz Festival in La Côte Saint André, Tamerlano (Irène) at the Poznan Festival with Les Ambassadeurs and Alexis Kossenko, Messiah with the Ensemble Matheus and Jean-Christophe Spinosi and Mendelssohn's Symphony Nr. 2 "Lobgesang" with Brussels Philharmonic and Hervé Niquet.