Born Josette Noëlle Andrée Claire Dagory, she began her career as an actress in 1919 at the age of five. Day was married in 1941 to famous French writer and director Marcel Pagnol, whom she met in January 1939. In 1946, she played her best-known role, alongside Jean Marais, as Belle in Jean Cocteau"s 1946 film Beauty and the Beast.
Her films include Allo Berlin? Ici Paris! Despite numerous parts in famous French films, Day ended her career as an actress in 1950 when only 36 years old.
In February 1959 while on cruise in the Pacific, she and Solvay met a Tahitian girl at a Papeete market named Hinano Tiatia, whom the couple took under legal guardianship and who was the center of Solvay"s inheritance dispute having not been formally adopted at the time of his sudden death in 1960.