The house seen in the movie in real life doesn't and never actually did exist. The film-makers could not find a suitable mansion to use for the film so at a cost of around $200,000, the production had a Victorian gothic mansion facade attached to the front of a much more modern dwelling in a Vancouver street. This construction was used for the filming of all the exteriors of the movie's Carmichael Mansion. The interiors of the haunted house were an elaborate group of interconnecting sets built inside a film studio in Vancouver.

Director Martin Scorsese included this movie on his Top 11 Scariest Horror Films of all time list.

The real life haunted house where the real life events apparently took place was the Henry Treat Rogers Mansion which was located at 1739 East 13th Avenue, Cheesman Park in Denver, Colorado. The house has since been demolished.

The movie is based on events which supposedly took place at Henry Treat Rogers Mansion in Denver, Colorado, whilst writer Russell Hunter was living there during the 1960s. The Chessman Park neighborhood in the movie is a reference to Cheesman Park in Denver, where the original haunting transpired.

Screenwriters [Diana Maddox] and William Gray spent around six months doing research for the picture which included copious newspaper articles on parapsychological encounters, over seven hundred books and almost two thousand case histories.

Actors Trish Van Devere and George C. Scott were married. Publicity for this picture stated they had made seven films together in their then eight years' marriage, this movie being their eighth.

First of two ghost story horror movies that veteran actor Melvyn Douglas made in a two year period right at the end of his film career. The other picture was Ghost Story (1981) his final film credit.

The meaning of the movie's "Changeling" title is defined as being, "a creature found in European folklore and folk religion. It is typically described as being the offspring of a fairy, troll, elf or other legendary creature that has been secretly left in the place of a human child. Sometimes the term is also used to refer to the child who was taken". It is the "swapped child" meaning of the term that is of relevance to this film's story.

Spanish filmmaker Alejandro AmenĂ¡bar has claimed in several interviews that this is one of his all-time favorite Horror movies, up to the point of inspiring several scenes of Thesis (1996) and The Others (2001).

Before Peter Medak was given the job, two British directors were considered; Tony Richardson declined due to creative differences.

This movie was the first film to win Best Picture in the Canadian Film Awards after its name was changed to the Genie Awards. The film was nominated for ten Genies and won eight.

Although Rick Wilkins is the credited film composer, the music box composition is actually written by Howard Blake. The unabridged composition is featured in his Lifecycle collection of 24 piano works in 24 keys.

Filmed from 4 December 1978 until 25 February 1979, but not released until March 1980.

Director Peter Medak said he was initially intimidated by stories of actor George C. Scott being difficult to work with. The only trouble Medak had with Scott on the set was when production managers accidentally knocked over a chess board on which Scott had been playing a game against himself for over two weeks.

First on-screen appearance of actor Joshua Jackson, when he was just several months old.

Though predominantly filmed in Canada, the picture was set in Seattle, USA where establishing shots were filmed. These included the Rainier Tower, the SeaTac Airport, the University of Washington's Red Square, and the Lacey V. Murrow Memorial Bridge. Some location filming was shot in New York. Most of the movie was filmed in Vancouver and its environs in British Columbia with Victoria in the same Canadian province also used. Interiors set at the university were shot in Toronto in Canada's province of Ontario.

In a featurette for the DVD release of the 1996 horror film 'Scream', actress Neve Campbell named The Changeling as the scariest film she had seen.

The drowning of Joseph in the bathtub was shot after principal shooting had wrapped.

Donald Cammell was initially slated to direct this film, but eventually left due to creative differences with the producers.

The name of the history group was the Seattle Historical Preservation Society. The name of the campus where Dr. John Russell (George C. Scott) taught music was the University of Seattle (though the interiors were filmed at the University of Toronto in Toronto, Canada).

The wheelchair sequence was filmed in Seattle, Washington.

George C. Scott learned how to play the piece of classical music that he plays on piano for the college students.

The opening scenes in New York City were shot first.

Tony Richardson was also considered to direct this film.

A finger thumb was used as the sound effect of the ball rolling down the stairs.

The score was composed in London, England.

There was an episode of Star Trek (1966) called Star Trek: The Changeling (1967). John Colicos appears in this film, and also as the Klingon in Star Trek Star Trek: Errand of Mercy (1967).

The same year, co-star Trish Van Devere was the main star in another haunted house movie, The Hearse.

Finnish certificate # 88322 delivered on 11-6-1980.