During filming in Montreal, two local punk rockers with Mohawk hairdos were hired as extras for a scene wherein they were to attempt mugging the newly awakened Kane (Van Peebles) in a dark alley. The two were paid a nominal fee, thanked for their services before shooting and the scene was dropped from the movie after they were seen taking drugs on the set and overheard plotting to kidnap Mario Van Peebles by driving away in the make-up RV with him in it.
The film is true to the original Highlander (1986) and ignores Highlander II: The Quickening (1991). In Highlander 2, Connor, Ramirez and the Immortals were aliens from the planet Zeist. In the original Highlander. Connor and Ramirez were not aliens from another planet and Highlander 3 takes place 8 years after the original film and is true to the original story and mythology.
Christopher Lambert enjoyed working with Mario Van Peebles so much the year before on the action film "Gunmen", that when this film presented itself, Lambert immediately suggested the role of Kane to Van Peebles, who accepted right away.
The original script for the film was radically different from the finished product in that the flashback sequences to place in early 17th century Scotland and early 18th century England. MacLeod had an Immortal friend in the script named Cavanagh who had similar aspects like Ramirez, The main villain in the script was named Kilvera. The script started depicting what happened with Connor after he buried Heather as well as a scene that revealed that he kills Jack the Ripper who was an Immortal as well.
When preparing for the sex scene between Connor and Alex, Christopher Lambert and Deborah Unger discussed about it and to be sure that they both felt comfortable about doing it and they decided to just go for it.
Michael Jayston is famous for playing The Valeyard, court prosecutor and a darker future incarnation of The Doctor in the 1986 season of Doctor Who (1963). This film was released 8 years after "Highlander", which was released in 1986.
In Spain Christopher Lambert's character is known as "Conner MacLeod" after that in the Spanish dubbed voice of Highlander (1986) Connor was turned in "Conner", and all later sequels were adapted in the dubbed voice according with it.