One of the first films (if not the first) to be shot using Panavision's Auto Panatar lenses that eliminated what was called "anamorphic mumps" in the wide-screen CinemaScope process where in close-ups an actor's face would widen horizontally. This innovation won Panavision its first Academy Award. Each lens cost $11,000 ($94,000 in 2017).
Director Mel Ferrer made a scouting trip to South America with nearly an hour of jungle footage filmed south of Orinoco and in the Parahauri Mountains, much of which was incorporated into the film. Twenty-five acres of back lot were converted to match the previously shot exteriors, incorporating 300 tons of turf, boulders, canoes, grass huts, blowguns, trees, and plants.
Vincente Minnelli originally started filming with Pier Angeli and British actor Edmund Purdom starring, but MGM chiefs hated the footage, and canceled the production.
Mel Ferrer had several snakes and birds native to the Venezuelan jungle captured and shipped to Hollywood for use in filming. He also brought a baby deer to the residence he shared with Audrey Hepburn, and they raised it for several months prior to filming so that it could be used in several scenes where Rima interacted with the forest creatures.