Gregory Peck later said regarding Robert Mitchum, "I had given him the role and had paid him a terrific amount of money. It was obvious he had the better role. I thought he would understand that, but he apparently thought he acted me off the screen. I didn't think highly of him for that."
The financial failure of Cape Fear (1962) ended Gregory Peck's company, Melville Productions.
At first, Robert Mitchum didn't want to do the film but finally relented after Gregory Peck and J. Lee Thompson delivered a case of bourbon to his home. His reply was, "Okay, I've drunk your bourbon. I'm drunk. I'll do it."
Gregory Peck, who produced the film, didn't like the original novel's title "The Executioners". When thinking of a new title, he decided that movies named after places tended to be very successful, so he looked at a map of the U.S. until he happened upon Cape Fear in North Carolina.
J. Lee Thompson had always envisioned the film in black and white prior to production. As an Alfred Hitchcock fan, he wanted to have Hitchcockian elements in the film, such as unusual lighting angles, an eerie musical score by Bernard Herrmann, closeups, and subtle hints rather than graphic depictions of the violence Cady has in mind for the family.
Polly Bergen suffered minor bruises in a scene where her character struggles with Cady. He was supposed to drag her through various doors on the set, but a crewmember mistakenly left all those doors locked, so that when Robert Mitchum forced Bergen through the doors, she was actually being used as a ram to push them open.
Robert Mitchum had a real life aversion to Savannah, Georgia, where as a teenager, he had been charged with vagrancy and put on a chain gang. This resulted in a number of the outdoor scenes being shot at Ladd's Marina in Stockton, California including the conflict on the houseboat at the end of the film.
The scene with the egg was added by J. Lee Thompson on the day of filming. Polly Bergen's reactions to Robert Mitchum rubbing the eggs on her was real.
Telly Savalas was screen tested for the role of Max Cady, but later played private eye Charlie Sievers.
This film contains one of the few instances of a correct depiction of what someone sees when looking through binoculars. In most films, what is shown resembles a sideways figure 8 (i.e. side by side magnified images, one for each eyepiece). But what one really sees is a single round magnified image, the same as what you see when looking into the eyepiece of a telescope.
According to Polly Bergen, Robert Mitchum cut his hand on a cabinet during their scene. "His hand was covered in blood, my back was covered in blood. We just kept going, caught up in the scene. They came over and physically stopped us."
Gregory Peck, Martin Balsam and Robert Mitchum appear in the remake, Cape Fear (1991): Peck as Cady's lawyer, Balsam as a judge, and Mitchum as a police lieutenant who suggests that Bowden use alternative means to get Cady to leave town.
In the source novel The Executioners, Cady was a soldier court-martialed and convicted on then Lieutenant Bowden's testimony for the brutal rape of a 14-year-old girl. The censors stepped in, banned the use of the word "rape", and stated that depicting Cady as a soldier reflected adversely on U.S. military personnel.
Charles Bronson, James Coburn, Charlton Heston, Jack Palance, and John Wayne were all considered for the role of Sam Bowden. Peck was a last-minute replacement for Heston, who was originally cast.
Rod Steiger wanted to play Max Cady, but he backed off when he heard Robert Mitchum was considering the role.
Jim Backus was set to play attorney Dave Grafton, but had to drop out due to conflicts with his new show Gilligan's Island (1964).
J. Lee Thompson originally wanted Hayley Mills to play Nancy Bowden, but Mills couldn't because she was contracted to Walt Disney.
Director J. Lee Thompson complained at the time that UK censor John Trevelyan had ruined the film by making extensive cuts, and the number of edits suggested ranged from 60 to over 100. Trevelyan later replied that he had made only 15 cuts, totalling around 6 minutes, with edits made to threatening dialogue and assault references, Cady's attack on Peggy, and all shots of him staring longingly at Nancy. All later UK video releases restored the cinema cuts.
In the scene in the police precinct, the cops listed on the duty roster are the characters from the 87th Precinct series of novels by Evan Hunter.
Gregory Peck and Robert Mitchum were contrasted personalities; Peck always preparing meticulously his roles,whilst Mitchum learned his lines only before a scene, because of his fantastic photographic memory.
Sam Bowden and Max Cady are the only characters to retain the same names in Cape Fear (1991).
Prior to its release, the film was heavily censored with many key elements of the fight scenes removed. Also deleted were numerous implications that Cady planned to sexually assault and then tortuously murder both Peggy and Nancy. These deletions were never restored.
Diane Taylor was portrayed by Barrie Chase, who played the part of the ditsy blonde, Doris Lenz, in White Christmas (1954).
As the producer of the movie, Gregory Peck supervised the editing, and took no advantage to put his character ahead of Mitchum's one.
Included among the American Film Institute's 2001 list of the top 100 Most Heart-Pounding American Movies.