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)

Tim Turner

Jason (voice) (uncredited)