Todd Armstrong
Jason
Nancy Kovack
Medea
Gary Raymond
Acastus
Laurence Naismith
Argos
Niall MacGinnis
Zeus
Michael Gwynn
Hermes
Douglas Wilmer
Pelias
Jack Gwillim
King Aeetes
Honor Blackman
Hera
John Cairney
Hylas
Patrick Troughton
Phineas
Andrew Faulds
Phalerus
Nigel Green
Hercules
John Crawford
Polydeuces (uncredited)
Ferdinando Poggi
Castor of Sparta (uncredited)
Ennio Antonelli
Dmitrius, Drummer on Argo (uncredited)
Harold Bradley
Guard in Palace (uncredited)
Aldo Cristiani
Lynceus (uncredited)
Eva Haddon
Medea (voice) (uncredited)
Doug Robinson
Eupaemus (uncredited)
Davina Taylor
Briseis (uncredited)
Tim Turner
Jason (voice) (uncredited)