Actor David Peel wore lifts in his shoes to make him the same height as actor Peter Cushing in the film. Peel, according to his bio at the time, was 5 foot 10. Cushing was six feet tall.
For the film's climax, Peter Cushing and director Terence Fisher had a difference of opinion over how the climax should be done. The actor wasn't happy about the idea of Van Helsing using powers of black magic in order to destroy Baron Meinster. Cushing explained that that went against everything his character represented.
To make the head vampire look more distinguished than Dracula, David Peel wore a full blonde hairpiece for his role of Baron Meinster.
The prop department put a lot of effort into making a realistic model bat, but it was lost, and had to be replaced on short notice. It explains the unconvincing model bat in the movie.
The ending was to have originally had the vampires destroyed by a swarm of bats. This ending proved too expensive to stage and shoot. The concept of this ending was recycled three years later for the climax of "Hammer's" "The Kiss of the Vampire (1963)."