While filming footage of the Argo off the coast of Italy, shooting was interrupted when a replica of the Golden Hind sailed into view. The British television series Sir Francis Drake (1961) happened to be filming in the same location. Producer Charles H. Schneer shouted, "Get that ship out of here. You're in the wrong century!" at the British crew, dispelling any tensions that arose from both shots being lost.
After Ray Harryhausen received the Gordon E. Sawyer Award recognizing his contributions of the film industry at the Oscars' Science & Technical Ceremony in 1992, Tom Hanks, the host of the event, said "Some people say Citizen Kane (1941) or Casablanca (1942). I say 'Jason and the Argonauts' is the greatest movie ever made."
This British / American film was filmed and released in the waning years of the Italian-produced sword-and-sandal / mythological muscleman movies. Many of those productions dealt with Jason. Most unusual for the time was the casting of British actor Nigel Green as Hercules. Although he was very tall, he lacked the bodybuilder physique that moviegoers were used to seeing for this character. Although film was not able to match the scale of spectacle of the European productions, the elaborate special effects by Ray Harryhausen gave it the look of a more expensive production, contributing to its box-office success.
The voice of Todd Armstrong, who played Jason, was dubbed by British actor Tim Turner. Turner's voice was well known as the narrator of the '60s Rank series "Look At Life"'. He was also the narrator of trailers in many British films in the '50s, '60s and '70s, including the one for this movie, and provided the voice of Dr. Peter Brady, the titular hero of the popular late '50s British TV series, The Invisible Man (1958).
Presumably in order to capitalize on the success of The 7th Voyage of Sinbad (1958), Ray Harryhausen originally conceived of the film as "Sinbad in the Age of Muses". The story would still have been set in ancient Greece and would have involved Sinbad joining Jason in the search for the Golden Fleece.
Contrasting with Bernard Herrmann's all-string score for Psycho (1960), the soundtrack was made without a string section. This leaves the brass and percussion to perform the heroic fanfares, and the woodwinds along with additional instruments (such as the harp) to dominate in the more subtle and romantic parts.
Curiously, for the first time in the history of the trade name of Ray Harryhausen's "Dynamation" process, this film never carried the "Dynamation" brand, even in the opening credits. Early publicity materials did, however, advertise this movie as being filmed in "Dynamation 90" (90 referring to the double 45-degree exposure in the sodium-light traveling matte process, used in this film, and some of Ray's previous films as well), but was reportedly dropped for being "too gimmicky". Additionally, the original pre-release prints carried the film's original title card, "Jason and the Golden Fleece" (which can be seen on the 1992 LaserDisc release by Criterion), before deciding on the film's eventual title, "Jason and the Argonauts", on March 1, three months prior to the film's release in early June.
In early press material, Mario Nascimbene was credited as the music composer of this film. This was because Nascimbene was considered, in case Bernard Herrmann turned down the offer to compose the score this film (which he didn't). In later interviews, Nascimbene claimed he never heard of the film (most probably meaning Herrmann accepted the offer before Nascimbene could be approached). He did, however, go on to compose the music score for another Ray Harryhausen film, One Million Years B.C. (1966), which was also directed by Don Chaffey (who directed this film).