The Collinwood scenes were filmed at the Lyndhurst Estate in Tarrytown, New York. The Lyndhurst Estate also housed Spratt Mansion, which had been used as the exterior of the "Old House" on the series, but was destroyed by a fire the year before "House of Dark Shadows" was shot.
This film was shot concurrently with the original Dark Shadows (1966) series. During the time of filming, the television program was in the middle of its 1970 parallel time story-arc. Major characters appearing in the film were temporarily written out of the TV series so that they would be available to shoot the movie.
Professor T.E. (Theodore Eliot) Stokes is named after two famous writers: T.S. Eliot and vampire novelist Bram Stoker.
For the old age make-up for Barnabas Collins, special make up artist Dick Smith used the bald head appliance that he had created for Dustin Hoffman in Little Big Man (1970) to save time and money.
First motion picture based on a daytime soap opera, in this case ABC's Gothic soap opera Dark Shadows (1966).