Revealing mistake: When the killer attacks Sid's bodyguards, the younger one has blood on his throat before the killer slashes it.
Visible crew/equipment: In the scene where Cici is killed, just before the killer throws her off the balcony there is a visible member of crew/stunt's head.
Continuity mistake: When Sydney is about to get in the car with the policemen, she has a rather large noticeable spot on her chin. In the following scenes, it is gone.
Continuity mistake: During the last stabbing of Maureen Evans, the killer puts his right arm around her and stabs her with his left; but from the back view, his left arm is around her, and he is stabbing her with his right.
Continuity mistake: Hallie takes the remote control off the top of the TV to turn it on. But later when they return in front of the TV to watch the news report, the remote is back on the top of the set. Also, the position of the video console which is also on top of the TV has changed, the position of the clothing on the chair next to the television has repositioned and lastly, the items on the window sill behind the TV set have completely changed.
Continuity mistake: When Sidney leaves her dorm room to head for the shower and Hallie follows, you can see the open wardrobe by the dorm door, and there is a jumper visible hanging from the wardrobe door. But when they walk back into the room to look at the news on TV, the jumper has moved and now there is a bag visible in front of it as well.