Continuity mistake: At the start, in shots from the stage towards the audience, all of the fires are lit, but in a closer shot of the audience near the front of the stage, at least one of the fires is out. During the final illusion shown at the end, the same shot or at least very similar to the one used at the beginning shows the same mistake again.
Continuity mistake: After Eisenheim has disappeared, literally, from stage, Uhl and the policemen search his office. There, Uhl finds Eisenheim's notebook with the design of the locket in it. There is a large tear in the middle of the paper. It disappears when the inspector looks at it again after he has found the locket in the Prince's barn.