Pat Hingle landed the title role, but before filming began, he became caught in a stalled elevator in his apartment building. He lost his balance while trying to crawl out and fell 54 feet down the shaft. He sustained massive injuries, including a fractured skull, wrist, hip and leg, and several broken ribs. He also lost his little finger on his left hand. Hingle spent much of the next year relearning how to walk and was forced to give up the part in order to recover from his horrific injuries.

200 stunt people and 1200 extras were used for the fire scenes.

A highly controversial novel in its day, no studio initially wanted to finance the film.

After this film was released, Burt Lancaster got a letter from a boyhood friend he had not heard from in years. The friend wrote him that Lancaster's part in this film was the closest to the way Lancaster acted in real life when they were kids.

Among the writers Gantry condemns in one of his sermons is Sinclair Lewis, the author of the book the film is based on.

Because of the success of the novel, it was adapted by Patrick Kearney into a play, which opened in New York City on 7 August 1928 and closed in September 1928 after 48 performances. The title role was played by Edward Pawley and Sharon Falconer was played by Vera Allen.

Director Richard Brooks did not want Shirley Jones for the role of Lulu Bains, but Burt Lancaster insisted. As a result, Brooks gave Jones no direction in the filming of a very difficult scene. Brooks eventually admitted to her that he couldn't see anyone else in the role.

For the film's debut on US network television, the subplot featuring Shirley Jones in her Oscar-winning role as a prostitute was largely excised. This was because Jones was then the star of the hugely successful and very wholesome The Partridge Family.

George F. Babbitt, the main character in Sinclair Lewis' 1922 novel "Babbitt", is a minor character in "Elmer Gantry". His character is the one most responsible for bringing Sister Sharon's revival to his home town of Zenith and just so happens to be the brothel's landlord.

In a hate-filled sermon, Gantry denounces a number of "heresies" including "Russellism". This is a reference to Charles Taze Russell, first president of the (current) Watchtower Bible and Tract Society, the legal organization used by Jehovah's Witnesses.

Sister Sharon is seen briefly outside a movie theater advertising a film. The title is not given but the stars names are given as Rudolph Valentino and Agnes Ayres, suggesting that the film is almost certainly The Sheik.

The character "Jim Lefferts" is clearly based on H.L. Mencken. Elmer Gantry mentions Mencken at about the 88th minute of the film.

To keep word from leaking out as to how the novel would be adapted to the screen, only the film's six major stars were given access to the complete screenplay.

When he first learned that Richard Brooks was interested in adapting his novel, Sinclair Lewis told him that he should change it significantly, advising him to read all the criticisms of the book and use them as a way to improve on it.