Many of the invasion scenes in Tokyo were edited from World War III Breaks Out (1960). The appearance of a giant billboard of Adolf Hitler has led some viewers to believe that the stock footage is taken from documentary footage of World War II Japan.
The film was released in 1961 in Japan and was later released in the United States on television. In 1998, the film was featured on an episode of Mystery Science Theater 3000.
Invasion of the Neptune Men is part of Japan's Tokusatsu genre, which involves films in the science fiction and/or superhero films that involve heavy use of special effects.