Born in Saint-Cast (Côtes-d'Armor), Aïtoff was admitted in the Conservatoire de Paris after having been introduced to Alfred Cortot.

From 1940, her name was often associated with that of the great conductor Charles Munch, of whom she became an important collaborator, known for her ability to teach singers their role, to reduce or transpose orchestral scores.

During the 1960s, she had the honour of being asked by Herbert von Karajan to ensure the singers' preparation to perform Debussy's Pelléas et Mélisande.

Until the beginning of this 21st century, Irène Aïtoff gave her advice and observations to many students, and worked with various renowned chefs, including Georg Solti and Charles Dutoit.

At the Théâtre Impérial de Compiègne in 1995, she was in charge of rehearsals of Auber's Le domino noir, a work that had totalled 1209 performances at the Salle Favart between 1837 and 1909.