Produced and distributed by Toho Co., Ltd., it is the first Honda-Tsuburaya collaboration filmed in both color and TohoScope, and stars Kenji Sahara, Yumi Shirakawa, Momoko Kōchi, Akihiko Hirata, Yoshio Tsuchiya, Susumu Fujita, and Takashi Shimura, with Haruo Nakajima and Katsumi Tezuka as Moguera.

In the film, Earth's defense forces unite to combat an extraterrestrial race that desires to intermarry with human women and settle on the planet.

Producer Tomoyuki Tanaka recruited science fiction writer Jōjirō Okami to develop the story, which Shigeru Kayama [ja] later adapted for Takeshi Kimura's screenplay.

An English dub of the film was produced by RKO Radio Pictures and distributed in the United States by Metro-Goldwyn-Mayer on May 27, 1959, where it grossed $975,000 and reportedly received mostly positive reviews.

Astrophysicist Ryoichi Shiraishi, his fiancée Hiroko Iwamoto, his sister Etsuko, and his friend Joji Atsumi attend a bon festival in a village at the foot of Mount Fuji.

Adachi hands him an incomplete report written by Shiraishi regarding a newly discovered asteroid he believed was once a planet between Mars and Jupiter, dubbed "Mysteroid".

After Atsumi briefs officials on what has been learned about the robot at the National Diet Building, astronomers witness activity in outer space around the Moon.

Although some Mysterians were able to escape to Mars before their planet was rendered uninhabitable, strontium-90 left the aliens' population deformed and they thus desire to interbreed with women on Earth to produce healthier offspring and keep their race alive.

The humans develop a new weapon, the Markalite FAHP (Flying Atomic Heat Projector), a gigantic lens that can reflect the Mysterians' weaponry.

"[6] Reflecting on the period of developing the film, Honda stated that he respected scientists, but "feared the danger of science, that whoever controlled it could take over the entire Earth.

Their interpreter was Heihachiro Okawa, an actor with a prolific eclectic career in Japan and overseas,[4] who played a bit part in the film as the Defense Headquarters External Relations Director.

[15] The Mysterians marks the first collaboration between Honda and special effects director Eiji Tsuburaya that was shot in anamorphic TohoScope, which the studio had just recently introduced.

[2] The film was first released in the USA by Metro Goldwyn Mayer in 50 Los Angeles theaters on May 27, 1959, the first half of a double bill with First Man Into Space, the publicity campaign being supervised by Terry Turner.

[21] Variety called it "well-produced", noting "special effects involving sliding land, quaking earth and melting mortars are realistically accomplished proving the facility with the Japanese filmmakers deal in miniatures.

"[23] Motion Picture Daily praised the film's effects, writing that "even the most jaded action fan will have to admit that some of the scenes of mass catastrophes, the seemingly endless sky and ground skirmishes and the ultra-modern 'Buck Rogers' settings have seldom, if ever, been equalled.

[25][26] The latter said that its "main weaknesses are a slight and confused plot, under-developed characterisation and artless acting" but praised the film's art direction and staging, calling them "possibly the most dazzling display of pyrotechnics in the genre to date.

[27] In a retrospective on Soviet science fiction film, British director Alex Cox compared The Mysterians to First Spaceship on Venus but described the latter as "more complex and morally ambiguous.

[29] In a retrospective review, Sight & Sound found its "space-age visuals and colourful design anticipate the spectacular fantasies Honda would go on to make for Toho in the [1960s], including Mothra, Godzilla vs.