Born Gabrielle l'Hôte, she studied at the Paris Conservatory with Louis Diémer and Marguerite Long and was awarded the first prize in piano at age 16.

She knew Maurice Ravel, Gabriel Fauré, Florent Schmitt and Moritz Moszkowski, and her interpretations were aided by their guidance.

As a teacher, Gaby Casadesus taught in the US, at the Salzburg Mozarteum, at the Académie Maurice Ravel in Saint-Jean-de-Luz and at the American Conservatoire at Fontainebleau.

In 1941, she played in New Jersey in a concert with Albert Einstein, in one of his rare appearances as a musician for an event to raise money for World War Two refugees.

She is buried with her husband and son, Jean in Recloses, department of Seine-et-Marne, approximately 73 kilometres (45 miles) southeast of Paris.