Development Happy Birthday to Me was produced by John Dunning and André Link, as a Cinépix production. Dunning and Link would team up again on another Canadian slasher,
My Bloody Valentine (1981), which went into production within a week of
Happy Birthday to Me wrapping; however,
My Bloody Valentine was actually released first, rushed to meet a February 11, 1981 release date in time for Valentine's Day. Keen to get their classier, bigger-budgeted
Happy Birthday to Me released, Dunning and Link quickly realized that gimmicks were being used up by other slasher movies in the wake of
John Carpenter’s
Halloween (1978) and
Sean S. Cunningham’s
Friday the 13th (1980). Dunning and Link felt that a slasher film centered around a birthday could have universal appeal. A third draft of the film's screenplay, dated April 1980, features a different plot twist in which Virginia is revealed to be the killer,
possessed by the spirit of her deceased mother. Although this ending logistically makes more sense than the ending that was filmed, the filmmakers thought that what was originally scripted was not climactic enough. Still, the majority of the film does point to this original ending, which indicates the switch came well into production. This version of the script also features a good number of scenes that were either never shot or rewritten, including some that show more clearly Alfred's love for Virginia and Virginia's difficult relationship with her father. The script was completely reworked by screenwriting team
Timothy Bond and Peter Jobin before production started. In the press material for the film, he stated: "What attracted me to this script was that the young people stood out as vivid, individual characters. The difference between a good chiller and exploitative junk, at least in my opinion, is whether or not you care about the victims".
Glenn Ford signed onto the project, portraying the role of Virginia's psychiatrist, as he was an admirer of director J. Lee Thompson.
Filming Happy Birthday to Me began filming in early July 1980. The film's make-up effects were done by special effects artist
Tom Burman (who replaced
Stéphan Dupuis just three weeks before the cameras were due to start rolling). Dupuis later did the duties on another bigger budget Canadian slasher,
Visiting Hours (1982), but left the production for undisclosed reasons. Ironically, in an issue of
Fangoria from 1981, Burman criticizes the level of gore in films at that time. Director Thompson became known for tossing buckets of blood about on the set of the film to increase the on-screen gore. According to producer
John Dunning, with the assistance of special effects man Tom Burman, Thompson "would be splashing blood all over the place".
Happy Birthday to Me completed filming in September 1980. Much of it was shot in and around
Loyola College in
Montreal, while the drawbridge scenes were actually filmed in
Phoenix, New York, just outside
Syracuse. During production, the film's screenplay underwent rewrites, including an entirely new ending that featured Ann as the real killer instead of Ginny. According to actress Melissa Sue Anderson, her character of Ginny "was so convincing as the good girl, they didn’t want to sacrifice the audience’s sympathy," leading screenwriters Timothy Bond and Peter Jobin to rework Saxton's screenplay. This mid-production alteration required the special effects team to craft a plaster cast of Anderson's face to design a latex mask, which Ann is revealed to be wearing in the finale. ==Music==