Roman Polanski was so faithful to the novel that he asked Ira Levin the date of the issue of the New Yorker in which Guy Woodhouse sees a shirt he wants. Levin confessed that he had made up the detail.
William Castle acquired the movie rights to the novel. Robert Evans of Paramount agreed to green-light the project if Castle did not direct. This was due to Castle's fame and reputation as a director of low budget horror films. Castle was allowed to make a prominent cameo appearance.
William Castle: man near phone booth.
Tony Curtis: voice on phone of the actor who is struck blind by a witch's curse so that Rosemary's husband can get an acting job.
Mia Farrow actually ate raw liver for a scene in the movie.
Mia Farrow does the vocals on the title-sequence lullaby.
Ira Levin felt Rosemary's Baby is "the single most faithful adaptation of a novel ever to come out of Hollywood." William Castle speculated the reasons for this were because it was the first time Roman Polanski had ever adapted another writer's work. Unaware he had the freedom to improvise on the book.
A scene was shot, but not used, of the characters attending an off-Broadway play. Mia Farrow's and Emmaline Henry's attend a performance of "The Fantasticks" and meet Joan Crawford and Van Johnson as themselves. Along with several other insignificant scenes, this was deleted to reduce the film's running time.
According to Mia Farrow, the scenes where Rosemary walks in front of traffic were spontaneous and genuine. Roman Polanski is reported to have told her that "nobody will hit a pregnant woman."
According to John Parker's recent biography of Jack Nicholson, Robert Evans suggested Nicholson to Polanski but, after their meeting, the director stated that "for all his talent, his slightly sinister appearance ruled him out".
Before the filming of the scene of Rosemary calling Donald Baumgart (the actor in the story who mysteriously goes blind), Mia Farrow did not know who would be speaking the lines. It was Tony Curtis, and in the scene Farrow shows slight confusion, finding the voice familiar but not able to place it. This confusion was exactly the effect director Roman Polanski hoped to capture by having Curtis read the lines.
Casting for this film presented its own problems: Polanski at first saw Rosemary as an "All-American Girl" and sought Tuesday Weld for the lead, but she passed on the role. Jane Fonda was then approached, but turned down the offer so she could make Barbarella in Europe with then- husband Roger Vadim. According to his memoirs, Polanski for a while had the idea of having his future wife Sharon Tate on the part of Rosemary, yet he desisted, thinking it would have been unethical. Other actresses considered for the part were Julie Christie, Elizabeth Hartman and Joanna Pettet. Robert Evans suggested Mia Farrow based on her TV work and her media appeal (at the time she was Mrs. Frank Sinatra). Both men wanted Robert Redford for the role of Guy Woodhouse, but negotiations broke down when Paramount's lawyers blundered by serving the actor with a subpoena over a contractual dispute regarding his pulling out of
Directed by Roman Polanski, whose pregnant wife actress Sharon Tate was murdered in 1969 by Charles Manson and his followers, who titled their death spree "Helter Skelter" after the 1968 song by The Beatles, one of whose members, John Lennon, would one day live (and in 1980 be murdered) in the Manhattan apartment building called The Dakota - where Rosemary's Baby had been filmed.
Entertainment Weekly voted this the tenth scariest film of all time.
In a scene where Rosemary is getting her blood drawn, Rosemary tells the doctor that she just saw the off- Broadway show "The Fantasticks." In that play, the parental figures arrange a "rape" of the ingenue, by a dark devilish character (named El Gallo), so a young man can save her, hoping that the young girl fall in love with the young man, marry him and procreate.
It was on the set of this film that Mia Farrow received divorce papers from then-husband Frank Sinatra.
Oscar-nominated editor Sam O'Steen would later direct the sequel, Look What's Happened to Rosemary's Baby.
Production chief Robert Evans has admitted that he simply used an offer to direct Downhill Racer to lure Roman Polanski from Europe. It was his intention to have Polanski direct this film all along.
Rosemary (Mia Farrow) says to Terry Gionoffrio (Angela Dorian), "I thought you were Victoria Vetri, the actress," to which Terry responds, "Everyone says that, but I don't see the resemblance." Victoria Vetri is Angela Dorian's real name.