During the first murder, the victim's location changes from shot to shot. By the end of the scene, she's in a completely different room.
The morning that Suzy arrives at the school, Miss Tanner tells Suzy that they were expecting her the night before. Suzy replies that she had arrived at the school the night before at 10 o'clock, but the door was locked. However, on her way up the staircase when Madame Blanc is explaining to the officers about the murdered girl's expulsion, Suzy interrupts to say she saw a girl leaving when she arrived at 11.
Twenty minutes in, Suzy accidentally knocks Sara's bag onto the floor in the changing room when she sits on the bench holding her dance shoes. Then, in a close-up, both women's hands can be seen picking up the bag's scattered contents. Then, in a two-shot, Suzy is still holding her dance shoes.
When the killer's hands are shown, they have huge, long, black fingernails. In the following scene where the victim is stabbed, the fingernails are now normal.
When Pat is drying off, there is some washing hanging on the line through the window. Then in an outside shot, the same washing is visible but now arranged differently.
Dario Argento's face can be seen reflected on the taxi's glass partition in the opening sequence. Assumed by many people to have been a mistake coming from a rushed shoot, Argento has gone on record to say it was intentional.
The cord used to pull the door from its hinges is visible.
The cord is visible on the bat as it flies from the closet.
When Suzy discovers Sara's long-dead body, Sara's neck can be seen pulsing.
At the 1hr9min mark when a character falls into rolls of barbed wire and gets trapped, with the barber wire cutting her flesh - a closer look reveals that all of the wire is plain, with no barbs at all.
The tagline is "The only thing more terrifying than the last 12 minutes of Suspiria are the first 92", which claims that the movie is 1 hour 44 minutes while it is actually 1 hour 39 minutes.
The spoken line ending with "...Gingivitis of the gums" is redundant. Gingivitis is a disease of the gums.
[German version only] On being dismissed by Madame Blanc, Mrs. Tanner utters "Of course" but her lips don't move. The words aren't included in the international version.
When Suzy is talking with the old psychiatrist at the convention centre and the camera slowly zooms in on the windows behind them and focuses on their reflections, Dario Argento is visible on the left side of the frame in a white T-shirt observing the scene and looking backing and forth. (More noticeable in the Blu-ray release.)
During the opening cab ride to the school, Suzy asks the cab driver "Has it been raining this hard for long?" As the driver turns back towards her, just outside the driver's window (on the left side of the shot), a pillar-like rotating piece of lighting equipment is clearly the source of the red and yellow strobe lighting during the entire scene.
When the main character arrives at the academy during the rainstorm, the flash-bulb producing the lightning can be seen reflected in the taxi's window.
In Germany, "Tanz Akademie" (as it appears on signage throughout the film) would be written as one word.
Characters sometimes say "Ciao!" to each other, even though none of them are Italian.
One of the dance students describes Daniel's guide dog as a wolfhound. The dog is a German Shepherd.
(76:13) In the English dubbed version, the Latin sentence cited by Prof. Milius is full of mistakes and thus virtually unintelligible ("Quandum ubique, quandum semper, quandum ad omnibus creditur est."). However, the line as intended by the author can be heard in the Italian version: "Quoddam semper, quoddam ubique, quoddam ab omnibus creditum est." Translated, it means, "If a thing is always, if a thing is everywhere, that thing is believed by everyone."
After discovering the crate full of rotten vegetables in the attic, several characters mistakenly refer to the maggots as worms.