The movie is very loosely based on Jack Engelhard's novel. While it does contain the story idea of "a million dollars for one night with a man's wife", most of the book focuses on Arab-Israeli intrigue.
Director Adrian Lyne and star Demi Moore often fought on set over her character, with Woody Harrelson trying to be mediator between the two. Lyne had argued that he wanted Moore to show vulnerability, while the actress defended herself. It was later while Lyne was editing the film that he realized she was portraying what he wanted all along, which he soon apologized to the actress.
Diana is reading "The Firm" by John Grisham, which Paramount Pictures soon afterwards filmed as The Firm (1993). The secretary at the real-estate office where she works is reading "Backlash", a book which criticizes director Adrian Lyne for his portrayal of women in previous films.
When Indecent Proposal was first released on VHS in 1993, the 1st pressing cassettes were colored green. Paramount Home Video did this five times (five movies, five colors). The other four were The Hunt for Red October (red); Ghost (white); The Godfather Part III (gold) and The Firm (blue).
In a scene towards the end of the film, David Murphy (Woody Harrelson) throws a punch - while outside in the rain - at John Gage (Robert Redford), but collapses before it reaches Redford. So his bodyguard Mr Shackleford (Seymour Cassel) gives Harrelson a fireman's lift, sets him down on a bed and smiles for some reason.