[1] Produced and distributed by Toho Studios, the film stars Akira Kubo, Atsuko Takahashi, Yukiko Kobayashi, Kenji Sahara, Yoshio Tsuchiya, and Yu Fujiki, with Haruo Nakajima portraying both Gezora and Ganimes.

Space Amoeba tells the story of amoeba-like extraterrestrials that hijack a space probe and, after crash landing on an atoll in the Pacific Ocean, create gigantic monsters from native lifeforms (a kisslip cuttlefish, stone crab and mata mata) for the purpose of conquering the Earth.

While on its outward journey to the gas giant, the probe is overtaken by the Space Amoeba, an amorphous parasitic extraterrestrial.

The probe returns to Earth and crashes into the South Pacific, where the Amoeba leaves the device and inhabits the body of a cuttlefish, causing it to mutate into what is called "Gezora".

When the survivors discover that Gezora is vulnerable to high temperatures, Kudo and his friends use a leftover Japanese World War II munitions bunker to set fire to the monster.

Ei Ogawa wrote the original script for this film in 1966 as a proposed joint production between Toho and UPA, under the title Great Monster Assault (怪獣大襲撃, Kaiju Daishūgeki).

This script was considerably more ambitious than the finished product, featuring alien monsters invading the Earth and submerging entire continents.

Assistant director Seiji Tani remarked that Space Amoeba was burdened by constant pressure from the studio to minimize the budget, and that as a result the staff was forced to rush through filming.

Producer Fumio Tanaka recalled that he had to personally transport the film negatives back to Tokyo on a prop plane.