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.
Polly Bergen suffered minor bruises in a scene where her character struggles with Robert Mitchum's character. He was supposed to drag her through various doors on the set, but a crewmember mistakenly left all those doors locked, so that when Mitchum forced Bergen through the doors, she was actually being used as a ram to push them open.
J. Lee Thompson originally wanted Hayley Mills to play Nancy Bowden, but Mills couldn't because she was contracted to Walt Disney. Thompson still wishes that he had Hayley Mills play Nancy.
According to Robert Mitchum, during the filming of the final fight scene between he and Gregory Peck, Peck once accidentally punched him for real. Mitchum, knowing that Peck didn't mean to and ever the professional, refused to break character and continued filming the scene. However, upon entering his trailer, Mitchum said he "literally collapsed" due to the impact of the punch and said that he felt it for days after wards. According to Mitchum: "I don't feel sorry for anyone dumb enough who picks a fight with him (Peck)."
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.
Max Cady was first offered to Ernest Borgnine.
The hotel where Mitchum takes Barrie Chase is "mother's house" from Psycho, where Martin Balsam met his demise two years earlier.
The trailer and radio spots are narrated by Universal regular, Jeff Morrow.
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.