Continuity mistake: In the scene where the shipwreck survivors are being rescued by Captain Nemo's divers, Nanette Newman is barefoot as she is carried into the submarine. In the shot immediately following, she is being carried into the sub by a diver and she is wearing full length black boots.
Continuity mistake: When the cabbie gets out of his cab, he closes the door, in later shots, you can see the door is open and he's standing between the open door and cab. Some shots show the door closed again.
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)