Producer Charles H. Schneer claimed that he chose this story after reading an article stating that Jules Verne's "Mysterious Island" was the most-looked-at book at public libraries.
Although produced by different studios, it is obvious that the exterior design of the "Nautilus" submarine as seen in the film was heavily influenced by Harper Goff's "half crocodile/half shark" Nautilus design in Disney's 20,000 Leagues Under the Sea (1954), especially with respect to the sub's top spar and rounded "eye" windows. In the original Jules Verne novels of "20,000 Leagues Under the Sea" and "Mysterious Island", the Nautilus is described as being rather plain, basically a cigar-shaped steel tube with very little outside detailing.
The scenes on the island were actually filmed on the coast of Spain.
The original novel does not contain any reference to giant or extinct animals or plants. Film makers decided to include this to make the movie more exciting, appearing ever since as the most recognizable and persistent aspect of every subsequent adaptation of this Jules Verne work. Interestingly, extinct fauna features predominantly in another Verne novel, Journey to the Center of the Earth.
Bernard Herrmann's main title score for this movie was used by Walt Disney for the Disneyland Railroad in California. It can be heard while the train passes through "The Primeval World" portion of the attraction between the Tomorrowland and Main Street stations.