Madame Curie

Greer Garson Marie Curie

Walter Pidgeon Pierre Curie

Henry Travers Eugene Curie

Albert Bassermann Professor Jean Perot

Robert Walker David Le Gros

C. Aubrey Smith Lord Kelvin

May Whitty Madame Eugene Curie

Victor Francen President of University

Elsa Bassermann Madame Perot

Reginald Owen Dr. Becquerel

Van Johnson Reporter

Margaret O'Brien Irene Curie - Age 5

James Hilton Narration Spoken By (voice)

Mariska Aldrich Tall Woman (uncredited)

Tony Carson Man at Accident (uncredited)

Ruth Cherrington Swedish Queen (uncredited)

Ray Collins Lecturer (voice) (uncredited)

Guy D'Ennery Professor (uncredited)

George Davis Cart Driver (uncredited)

Harold De Becker Professor (uncredited)