Continuity mistake: Frankenstein buys a sprig of freesias as a buttonhole: two yellow flowers and a purple. The sprig immediately changes into two purple flowers and a yellow. When Frankenstein meets Mrs Brandt and they go into the drawing room, the flowers are two purples and a red with yellow centre. Once in the cellar to see Mr Brandt, the red goes, and a yellow is back with two purples. (00:57:45 - 01:03:55)
Continuity mistake: In the scene where the grave robbers are loading Edward's coffin onto their cart, the coffin lid can be visibly seen bouncing up. Yet in the next scene where Christopher Lee is attempting to open Edward's coffin, he has to use force to open it.
Continuity mistake: When Carl lets his dog out of the bag, in the close-up there's a shadow on Rod Steiger's boot, and a shadow of something or someone standing between him and the camera: both are gone in the following shot, when the dog runs across the lawn (and 'knocks aside' the camera). (00:08:20)