"Clouzot does it, all right; his Grand Guignol techniques are so calculatedly grisly that they seem silly, yet they succeed in making one feel queasy and sordid and scared."
— Pauline Kael, 5001 Nights at the Movies

"... prior to Alfred Hitchcock’s Psycho, Clouzot’s eerie masterwork was considered the most frightening and artistic horror picture ever made. In fact, just as Hitchcock was a major influence on France’s master of suspense, Hitchcock admitted an equal debt to Clouzot, and not just because they had similar disrespect for actors (whereas Hitchcock called them 'cattle,' martinet Clouzot called them 'instruments'). Not only can we see traces of Psycho throughout Diabolique—note the many similar plot elements and story twists, suspense devices, shocks, quirky characters, and morbid humor—but Hitchcock even borrowed Clouzot’s successful ploy of insisting no one be admitted to theaters once the film began. ... As always, his film is strongly acted, strikingly paced for tension and suspense, and exhibits a perverse nastiness of character and environment that is oppressive and unsettling. It is a film where the heroine—the nicest person in the story—plans a cold-blooded murder; an entire scene at the school centers around the serving and eating of spoiled fish (rumor has it that the director actually made his actors eat the fish so they’d better understand the nature of the school and the characters); the dilapidated school, rowdy boys, and terrible teachers are a matched set; and where water, a symbol of purity and birth/life, is equated with death (as in Psycho). Diabolique is most definitely the work of an angry artist who spent several years of his adult life in sanitariums recovering from his illness but not his cynicism."
— Danny Peary

"... the suspense that has been built up is dissipated in a virtuoso display of plot-twisting, which leaves the audience reeling, but destroys the credibility of all that has gone before."
— Roy Armes, French Cinema

"On a voulu voir longtemps dans Les Diaboliques, que les scènes d'horreur, l'orchestration de la peur par une mise en scène 'coup de poing'. Mais il y a aussi le réalisme psychologique noir, qui, dès Le Corbeau, fut un signe distinctif du cinéaste, de sa misanthropie, de ses doutes sur la nature humaine et de son gout des situations troubles."
— Jacques Siclier