This movie is based on actual events that occurred between November 1966 and December 1967 in Point Pleasant, West Virginia.
The name of the expert on paranormal activity is Leek, the reverse of paranormal expert and author of the novel on which this movie was based, John A. Keel.
Lakeshore Entertainment cut two million dollars out of the budget just days before shooting began. Director Mark Pellington was furious, having vowed not to make the same concessions that plagued his previous movie, Arlington Road (1999).
The scene where Indrid Cold is seen for the first time in full wasn't done with CGI. Bill Laing was simply shot in blurred vision.
DIRECTOR CAMEO (Mark Pellington): The bartender, also the voice of Indrid Cold during the phone call.
The clock radio in John Klein's (Richard Gere's) motel room reads: 6:14. It's a Biblical reference to John Chapter 6 verse 14, which reads, "This is indeed the prophet who is to come into the world."
The news station, WOWK 13, shown during the Charleston scenes is the actual news station for the Charleston-Huntington area.
Contrary to popular belief, the Mothman wasn't originally described as a moth-like creature by the witnesses. At the time, the creature was described as half-bird and half-man. They also claimed that the creature had feathers and would make screeching noise.
The Mothman from 1966 and 1967 was originally named after the title of Batman (1966).
When John Klein (Richard Gere) has his first encounter with the Mothman, it results in a car accident when his car collides with a tree. The street is Bartlett Street in Squirrel Hill in Pittsburgh, Pennsylvania. The traffic signal they're approaching was put in for filming, and is no longer there.
Michael Gambon, John Hurt, David Suchet, and Charles Dance were considered for the role of Alexander Leek.