Originally, the film wasn't going to include the giant walrus Magma. However, producer Tomoyuki Tanaka insisted that the monster be put into the film and forced director Ishirô Honda to include it despite him being against it.
Magma or Maguma is one of the few monsters in the Toho menagerie to not appear in any films in the Godzilla series. There were plans to have the monster appear in Les envahisseurs attaquent (1968) guarding the aliens' base, but it was decided not to include him. The Magma suit was however reused for the monster Todora in the series Urutora Q (1965), with added whiskers to make it look more walrus-like.
Strangely, the monster Magma or Maguma is said to be a reptilian creature despite resembling a walrus. The script didn't specify any details about the creature, only that it was meant to be a reptile. Not wanting to simply do a rehash of Godzilla, Ishirô Honda had it changed to a giant walrus instead. Despite this change, the Toho studio kept insisting that Magma was a reptile as stated in the original script, referring to the monster as such in various Godzilla encyclopedias released decades after the film.
Gorath was released theatrically in Japan on 21 March 1962 where it was distributed by Toho. It was released in the United States as Gorath by Brenco Pictures through Allied Artists Pictures with an English-language dub on 15 May 1964. The film was double-billed in the United States with The Human Vapor.
The original Japanese version has never being made available outside of Japan, with only a bootleg copy accompanied by false subtitles being available. In 2021 dedicated fans took it upon themselves to finally give the film a proper translation and preserve the original story lost in the dub and false subtitles.