Anachronisms: Set in 1927, when Elmer is on railway tracks after jumping from a moving train, a 1950s Ford can be seen in the distance.
Continuity: The straps on Lulu Bains' dress.
Continuity: The first time we see Lulu, she leans on the back of a chair, a newspaper in her hand, and her right shoulder strap has fallen down. In the next shot her left shoulder strap is down instead.
Continuity: Sharon gets into the car, behind the wheel and tells Elmer to get in, which he does, on the passenger side. In the next shot, the car goes by with Elmer driving.
Continuity: While Elmer is briefing the staff before the Zenith rally, he refers to an opening "tonight". In the next scene (presumably, on the same day or later), Jim asks Sharon if she is nervous about "opening *tomorrow* night."
Revealing mistakes: When Elmer enters Lulu's hotel room, you can clearly see the trip wire that is going to pull the vase off the mantlepiece and scare the cat.
Audio/visual unsynchronized: The voice-over of the Battle Hymn of the Republic does not match the video during the Revival.
Continuity: When Elmer Gantry is shown walking into the town after jumping off the freight train, the billboard advertising Sister Sharon's revival shows dates of Dec 1-12. A few scenes later in the general store where he looks closely at a wall poster of Sister Sharon, the calendar next to it shows June 3.
Errors in geography: The location where Sister Sharon confronts the police captain and fire chief over erecting her tent is purported to be in Lincoln Nebraska. The opening part of the scene shows mountains in the background. There are no mountains around Lincoln.
Errors made by characters (possibly deliberate errors by the filmmakers): At the newspaper office meeting, Elmer Gantry refers to Christ' miracle of feeding the 5,000 with five fishes and two loaves of bread. According to the Gospels, it was five loaves and two fishes.
Continuity: The first time Gantry is in Lulu's room and she is staging the blackmail photos, she puts the money he hands her into the top of the stocking on her right leg while he stands on her right side next to her right leg. When we are later shown the photograph as published in the newspaper, Gantry is still standing on her right side next to her right leg, but Lulu is inserting the money into the top of the stocking on her left leg rather than her right leg.
Anachronisms: The movie is supposed to take place in 1927. When Lulu is waiting for Elmer, she switches on a small electric bakelite radio on the dresser. In 1927 there were no electric radios, only large wood battery operated radios. The small radio she switches on is from around 1938-1940.