George C. Scott wears an eye patch over his left eye during the final half hour of the film which was due to the infection caused by the contact lens used earlier in the film. The eye was not quite healed and had to wear it to complete the filming of his scenes.
Prophetically, a few years before she was cast in the film, six-year-old Drew Barrymore's mother thought that Drew resembled the girl on the source novel's paperback dust-jacket. Drew once said: "My mom had seen this book at the grocery store with a picture of a little girl on it and she said, 'Gee, this looks kinda like you'. She said it was okay if I bought it, and so I did. When I read it, I came into the kitchen where my mom was making dinner and said: 'I'm the Firestarter. I'm Charlie McGee!' But she didn't know what I was talking about."
In a 2010 interview, director Mark L. Lester confirmed that this was the most difficult film that he ever made. He said, "That was all practical [effects]. The fireballs you see, that's not CGI. Back then, we actually created fireballs that could fly through the air, they were on a wire and could crash into buildings. We had people on fire that were on trampolines that had to flip through the air. It was very dangerous. All the effects were done right on the set. It was a pretty intense thing to do then."
Martin Sheen took over at a late stage from Burt Lancaster, who had to withdraw following heart surgery.
This film was originally going to be directed by John Carpenter and Bill Lancaster, who wrote the screenplay for The Thing (1982), even wrote a draft for this film. But, according to Carpenter, Universal executives removed both of them from the project in the wake of the box-office and critical drubbing they received for The Thing. Carpenter had reportedly talked to Darwin Joston about taking on the role of John Rainbird, which was ultimately played by George C. Scott. Thirty eight years later, Carpenter, along with son Cody Carpenter and frequent collaborator Daniel A. Davies, would be brought on to compose the score for the Firestarter (2022) remake.