Production notes

Director Henri-Georges Clouzot's wife, Véra, initially drew his attention to the Boileau-Narcejac novel on which the film is based. Clouzot read it through the night and optioned the rights the following morning. He and his brother Jean (who took the pseudonym Jérôme Géronimi) spent 18 months adapting the novel. In the book, the action takes place between Enghien-les-Bains and Nantes but Clouzot transposed it to Saint-Cloud and Niort, his own birthplace. He was not particularly interested in the insurance scam that was the criminal motive in the book. He switched the gender of the murderers and invented the private-school setting. Film historian Susan Hayward suggests that the gender switch made by Clouzot was caused not so much by censorship considerations (in the source novel, Lucienne and Mireille turn out to be a pair of lesbian lovers), but by his desire to create a sizeable role for his wife. The book has only one principal female character, Lucienne, since the supposed victim, Mireille disappears early on. Véra, with her distinctly feminine demeanor, was ill-suited for the role of Lucienne (called Nicole in the film). So in Clouzot's script, Mireille (now named Christina) is the character who has a weak heart, and is the object of manipulation of her husband Michel and his mistress Nicole. Clouzot also followed the convention that the culprits should be exposed by the detective in the end (another departure from the novel, where the authors let them get away).

Véra was the first to be cast in the film in the role of Christina. Director Clouzot cast Simone Signoret opposite her in the role of Nicole; he previously directed Signoret's husband Yves Montand in The Wages of Fear, and the two couples became friends. Clouzot was also aware of his wife's Vera's limitations as an actress, and sought someone to lend her support in such a demanding role. Signoret signed an eight-week contract but the shooting actually took 16 weeks. She ended up being paid for only eight weeks of work despite staying until the end of the filming because she neglected to read the small print. Signoret's co-star Paul Meurisse also recalls in his memoirs that the actress was further bemused by Clouzot's constant attempts to find clever ways of lighting Vera's face while muting the light on Signoret so she would not upstage his wife. Clouzot had known Meurisse since 1939, when the latter was attempting to pursue a singing career. Clouzot then was trying to sell his song lyrics to Edith Piaf, Meurisse's lover at the time. By the late 1940s, Meurisse had become an established stage and screen actor, known for the roles of "icy and sophisticated villains," and he seemed a natural choice for the role of Michel. The film featured two Clouzot regulars: Pierre Larquey as M. Drain and Noël Roquevert as M. Herboux. Michel Serrault made his screen debut as M. Raymond, one of the schoolteachers. Charles Vanel—who previously co-starred in Clouzot's The Wages of Fear—was cast as the seemingly inept Inspector Fichet. Clouzot also auditioned 300 children and selected 35. Among them were Jean-Philippe Smet (the future Johnny Hallyday), Patrick Dewaere's brother Yves-Marie Maurin, and Georges Poujouly, who previously received acclaim in René Clément's Forbidden Games.

The filming began on 18 August 1954 and finished on 30 November the same year. Clouzot asked his assistant Michel Romanoff to find a suitable filming location for the boarding school. The latter discovered a decrepit chateau in L'Etang-la-Ville between Saint-Cloud and the Bois-du-Boulogne. The building and its surroundings matched the director's vision perfectly since they projected the desired mood of decay and neglect, featuring an adjacent swimming pool that was dirty and full of slime. Clouzot spent five weeks shooting at this location. The screenplay placed Nicole's apartment in Niort, but the actual house used for filming was in Montfort-l'Amaury, just opposite the building that previously appeared in Clouzot's Le Corbeau. The morgue scenes were shot inside an actual mortuary at the Institut Médico-légal in Paris. The rest was filmed at Saint-Maurice Studios southeast of Paris, which took an additional nine weeks. The interior sets were designed by Léon Barsacq. Cinematographer Armand Thirard used two camera crews to speed up the shooting that was falling behind schedule. Despite his efforts, the filming took twice longer than the projected 48 days. Thirard shot the majority of the film using predominately medium shots and close-ups to accentuate a sense of anxiety and claustrophobia. The film's central murder sequence in which Meurisse's character is drowned in the bathtub was shot over a period of two days. To prevent the actor from becoming ill, the crew filled the bathtub with hot water for each take, and in between shots, Meurisse was redressed in dry clothes and given whisky toddies. Originally the film was to be called Les Veuves (The Widows) but this was deemed unmarketable. Eleven weeks into filming it was changed to Les Démoniaques. Eventually it was renamed Les Diaboliques but this title was already used for a collection of short stories by the 19th-century writer Barbey d'Aurevilly. Clouzot was permitted to use this title but only on the condition that he give the author a proper mention. He did it by opening the film with a quote from the preface to d'Aurevilly's work: "A portrait is always moral when it is tragic and shows the horror of the things it represents."

Les Diaboliques created a sensation upon its French release and was a success at the box office with 3,674,380 admissions in France alone. It ranked seventh place for final audience figures in France by the end of the year. The film was also a major box-office hit in the United States, with estimated ticket sales of $600,000 (equivalent to $7.1 million in 2025) by September 1956, making it the highest-grossing French film in the country's history at that time.

Critical reception for Les Diaboliques was highly favorable in both France and the United States. Bosley Crowther gave the film an enthusiastic review in The New York Times, calling it "one of the dandiest mystery dramas that has shown here" and "a pip of a murder thriller, ghost story and character play rolled into one". He added "the writing and the visual construction are superb, and the performance by top-notch French actors on the highest level of sureness and finesse." The Chicago Daily Tribune wrote, "If you like a good mystery and can stand it fairly morbid and uncompromising as to detail, this is one of the best offerings in a long time." The reviewer added, "You may suspect, as I did, one of the answers as the film nears its finale, but if you solve it all, you've missed your profession." Variety was more critical: “Although this has a few hallucinating bits of terror, the film is primarily a creaky-door type of melodrama. Its macabre aspects and lack of sympathy for the characters make this a hybrid which flounders between a blasting look at human infamy and an out-and-out contrived whodunit." Dorothy Masters of the New York Daily News praised the lead performances of Signoret, Clouzot, and Meurisse, and gave the film a three and a half out of four star-rating, summarizing: "The arch fiends of hell couldn't have plotted better than Pierre Boileau and Thomas Narcejac... The horrors, psychological and physical, make this a shocker worthy of the devil himself." Hortense Morton of the San Francisco Examiner praised the film as "a super suspense yarn knitted together with a deft Gallic touch. Madam Dufarge [sic] couldn't do better, and a splendid, very splendid cast, sees that no dramatic stitches are dropped." The National Board of Review named it among the best foreign films of 1955, and called it "a genuine thriller—a shocking, satisfying chunk of Grand Guignol psychological suspense." Reviews from British film critics were less favorable. Milton Shulman in the Sunday Express accused the film of "calculated malevolence", and commented that "it is no trick to sicken an audience by such blunt methods as these." C. A. Lejeune in The Observer called it "extremely clever and very horrid," and complained about "a vogue at the moment for the horrid in entertainment." Reg Whiteley in the Daily Mirror described it as "a suspenseful but sordid slice of French life," and exclaimed: "Just how horrible can films get?" Alan Brien of The Guardian Journal panned the film, writing that "as the work of a minor Hitchcock," the film would be "eminently acceptable. From Henri-Georges Clouzot, the director of The Wages of Fear, it must be reckoned a disappointment." Roger Ebert, reviewing the film during its 1995 re-release, wrote: "The famous plot of the movie usually deceives first-time viewers, at least up to a point. The final revelations are somewhat disappointing, but Clouzot doesn't linger over them. The most disturbing elements of the movie are implied, not seen." Time Out commented that the film "makes for a great piece of Guignol misanthropy" where "everyone is in the end a victim, and their actions operate like snares setting traps that leave them grasping for survival." On the review aggregator website Rotten Tomatoes, 95% of 85 critics' reviews are positive, with an average rating of 8.6/10. The website's consensus reads: "Cruel, dark, but undeniably effective, Diabolique is a suspense thriller as effective as Hitchcock's best work and with a brilliant twist ending."