Marie Sklodowska
Greer Garson
Prof. Pierre Curie
Walter Pidgeon
Eugene Curie
Henry Travers
David Le Gros
Robert Walker
Professor Jean Perot
Albert Bassermann
Professor Jean Perot
Albert Basserman
Irene at Age Five
Margaret O'Brien
Reporter
Van Johnson
Lord Kelvin
C. Aubrey Smith
Madame Eugene Curie
May Whitty
President of University
Victor Francen
Dr. Becquerel
Reginald Owen
Madame Perot
Elsa Bassermann
Mme. Perot
Elsa Basserman
Narration Spoken By (voice)
James Hilton
Professor Roget (uncredited)
Lumsden Hare
Tall Woman (uncredited)
Mariska Aldrich
Board Member
Charles Trowbridge
Man at Accident (uncredited)
Tony Carson
Board Member (uncredited)
Edward Fielding
Swedish Queen (uncredited)
Ruth Cherrington
Board Member (uncredited)
James Kirkwood
Board Member (uncredited)
Nestor Eristoff
Lecturer (voice) (uncredited)
Ray Collins
Professor (uncredited)
Guy D'Ennery
President of Businessman's Board (uncredited)
Moroni Olsen
Cart Driver (uncredited)
George Davis
Dr. Bladh (uncredited)
Alan Napier
Madame Michaud (uncredited)
Almira Sessions
Professor (uncredited)
Harold De Becker
Assistant Tailor (uncredited)
Franz Dorfler
Nurse
Dorothy Gilmore
Eve at 18 Months (uncredited)
Gigi Perreau
Woman at Accident (uncredited)
Justine Duney
Man at Accident (uncredited)
Tay Dunn
Cart Driver (uncredited)
William Edmunds
King Oscar
Wyndham Standing
Man at Accident (uncredited)
Al Ferguson
Prof. Constant (voice) (uncredited)
Howard Freeman
Proud Papa
Michael Visaroff
Perot Granddaughter (uncredited)
Linda Lee Gates
Singing Professor
George Meader
Perot Granddaughter (uncredited)
Marie Louise Gates
Lucille (uncredited)
Lisa Golm
Seamstress (uncredited)
Ilka Grüning
Driver
Ray Teal
Wedding Guest (uncredited)
Noel Mills
Son (uncredited)
Teddy Infuhr
Woman at Accident (uncredited)
Isabel La Mal
Photographer (uncredited)
Leo Mostovoy
Master Michaud
Dickie Myers
Bit Part (uncredited)
Gene Lockhart
Monsieur Michaud (uncredited)
Francis Pierlot
Businessman (uncredited)
Miles Mander
Singing Professor (uncredited)
George Meader
Jewelry Salesman
Marek Windheim
Master Michaud (uncredited)
Dickie Meyers
Doctor
Eustace Wyatt
Woman at Accident (uncredited)
María Pagés
Isabelle Lamore
Businessman
Frederic Worlock
Woman at Accident (uncredited)
Nita Pike
Nurse (uncredited)
Dorothy Raye
Businessman
Arthur Shields