- Acting for Two: In a cut scene, Wolfgang Kileling also played Gromek's brother.
- Creative Differences: This film marked the end of Alfred Hitchcock's partnership with Bernard Herrmann. Hitchcock and Universal wanted an upbeat pop/jazz score for the film, as opposed to Herrmann's typical style. Herrmann's revised score was rejected and Herrmann quit the film.
- Creator Backlash: Alfred Hitchcock didn't like this film very much, as he had an unhappy experience making it and was unhappy with Paul Newman's performance. In fact, he was so unhappy with this film that he decided to not to make a trailer with his appearance in it. After a while Hitchcock ignored his stars and centered his attention on the colorful international actors who played supporting roles in the film. This at least came with an upside: Lila Kedrova was Hitchcock's favorite among the cast; he ate lunch with her several times during filming and invited her home for dinners with his wife. Although the length of the film was shortened in post-production, Hitchcock left intact Countess Kutchiska scenes in the final film.
- Newman was displeased enough during production that he sent Hitchcock a long memo expressing his problems with the film. Hitchcock, not used to an actor asserting himself like that, had strained relations with Newman afterwards.
- A notable consequence of Hitchcock's displeasure with being forced to cast Newman and Julie Andrews is that his final three films all featured an Ensemble Cast rather than A-list stars
- Deleted Scene: A scene showing Gromek's brother was cut. In it he shows Michael Armstrong, who has just killed Gromek, a picture of Gromek's three children. It was believed that this would have shifted the audience's sympathy away from Michael to the dead man. Unfortunately, a close-up of the brother cutting a sausage with a knife similar to the one used in the murder, a characteristically Hitchcockian shot, was also lost.
- Troubled Production: Hitchcock was not entirely happy with the casting of this film. He wanted Cary Grant as the male lead, with either Eva Marie Saint or Tippi Hedren as the leading lady. Grant turned him down. He was preoccupied with filming Walk, Don't Run and intended to retire after that. Universal Pictures executives insisted on casting Newman and Andrews, in the belief that more famous (and also more current) stars would result in better box office results. Newman had starred in several hits the 1950s. Andrews was a younger actress who was mostly known for theatrical work prior to starring in Mary Poppins. After that film turned to a box office hit, she became one of the most famous actresses of the 1960s. Hitchcock and Newman had a difficult working relationship, Andrews felt borderline mistreated by Hitchcock due to the way he "neglected" her (as opposed to fetishizing her the way he usually did to his leading ladies), and the chemistry between the leads was rather poor. Nevertheless, it was a modest box office hit.
- Wag the Director: Alfred Hitchcock and Paul Newman had a problematic working relationship, as Hitchcock was unfamiliar with Method Acting. Newman questioned Hitchcock about the script and the characterization throughout filming, to which Hitch quipped that his salary was his motivation. Newman insisted that he meant no disrespect towards Hitchcock, and once said,"I think Hitch and I could have really hit it off, but the script kept getting in the way."
- What Could Have Been:
There was an ending written which wasn't used, but I rather liked it. No one agreed with me except my colleague at home (his wife Alma). Everyone told me that you couldn't have a letdown ending after all that. Paul Newman would have thrown the formula away. After what he has gone through, after everything we have endured with him, he just tosses it. It speaks to the futility of all, and it's in keeping with the kind of naiveté of the character, who is no professional spy, and who will certainly retire from that nefarious business.
- Alfred Hitchcock originally wanted to cast Cary Grant as Professor Michael Armstrong, but Grant (62 at the time) told him he was too old. In a 1986 interview, Anthony Perkins claimed that Hitchcock wanted to cast him, but the studio was adamantly against the idea.
- Hitchcock had originally had Samantha Eggar in mind for the lead role. Tippi Hedren and Eva Marie Saint were also considered.
- According to Norman Lloyd, Universal Pictures wanted Henry Mancini to do the score, so they pressured Sir Hitchcock not to hire Bernard Herrmann.
- According to the book It's Only a Movie, Hitchcock said:
Trivia / Torn Curtain