- Paul Newman as Professor Michael Armstrong
- Julie Andrews as Sarah Sherman
- Lila Kedrova as Countess Kuchinska
- Hansjörg Felmy as Heinrich Gerhard
- Tamara Toumanova as Ballerina
- Wolfgang Kieling as Hermann Gromek
- Ludwig Donath as Professor Gustav Lindt
- Günter Strack as Professor Karl Manfred
- David Opatoshu as Mr. Jacobi
- Gisela Fischer as Dr. Koska
- Mort Mills as Farmer
- Carolyn Conwell as Farmer's Wife
- Arthur Gould-Porter as Freddy, the Bookseller
- Gloria Gorvin as Fräulein Mann
- Robert Boon as Professor Winkelmann
- Peter Bourne as Professor Olaf Hengström
- Linda Carol as Dancer
- Rico Cattani as Heinrich, Escape Bus Driver
- Andrea Darvi as Gretl Koska
- Maurice Doner as Hugo, Baggage Manager
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- Harold Dyrenforth as Otto Haupt
- Horst Ebersberg as East German Interpreter
- Ben Frommer as Sceptical-Looking Airline Passenger
- Sasha Harden as Border Guard
- Joe Harris as Ballet Member
- Mischa Hausserman as Idealistic Young Man
- Alfred Hitchcock as Man in Hotel Lobby with Baby
- Erik Holland as Hotel Travel Clerk
- Nancy Kilgas as Ballet Member
- Peter Lorre Jr. as Taxi Driver (uncredited)
- Jan Malmsjö as Swedish Photographer
- Hedley Mattingly as Airline Official
- Norbert Meisel as Factory Manager
- Frank Oberschall as Airport Security Man
- Gerd Rein as East German Arresting Officer in Bus Sequence
- Gene Roth as Guard in Post Office
- Norbert Schiller as Professor Gutman
- Lyle Sudrow as Swedish Captain
- Wilhelm von Homburg as Blonde Twin in Bus
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