Joan Rivers is portrayed in this film by her real-life daughter Melissa Rivers. Director David O. Russell asked Melissa for input on dialogue written for her mother, particularly in the scene where she gives Joy clothing feedback.
Despite earlier reports, this movie is not a biography of Joy Mangano. Annie Mumolo's original script was based on Mangano, an Italian-American inventor and entrepreneur known for inventions such as the self-wringing Miracle Mop and Huggable Hangers. She is the President of Ingenious Designs, appears regularly on U.S. television shopping channel HSN, and holds more than 100 patents. When David O. Russell came onto the project, he added many more supporting characters, and interwove Mangano's original biography with stories of other women changing their lives. Russell admitted he was in no hurry to meet Mangano in real-life during filming, because he wanted to make the movie his own way. He only spoke to Mangano on the phone. Joy's last name is never mentioned in the film, and she is not a native of Smithtown, New York, on Long Island's north shore.
Jennifer Lawrence wore wigs and hairpieces for the majority of filming. While doing Joy's haircut scene, she accidentally snipped some of her own hair as well as the fake hairpieces. The whole haircut was done in one take.
Among the changes that David O. Russell made to the original biographical story of Joy Mangano that was featured in Annie Mumolo's script was adding Joy's half-sister, Peggy, who is entirely fictional. Terry is a composite of several people in Joy Mangano's life. In real life, Joy's ex-husband, Tony Miranne, was a fellow business student and former classmate at Pace University, not a Venezuelan singer. Russell has stated several times that he does not consider his film to be a biographical film of Mangano, as it was originally intended to be, when Mumolo wrote her script, which was later heavily changed by Russell.