Screenwriter J. Michael Straczynski first learned of the story of Christine Collins from an unnamed source at Los Angeles City Hall. The source had stumbled across case files regarding the Wineville Chicken Coop Murders among other discarded documents scheduled for destruction. Straczynski took the files and became obsessed with the case, doing extensive research over the course of a year. He tried to make it into a television project, but never found a solid way to do that. Virtually every event depicted in this movie appears as cited in legal documents, with dialogue often taken verbatim from court transcripts. Straczynski wrote his first draft of the screenplay in only 11 days.
The title refers to a European folk legend. Supposedly, fairies, elves, trolls, or even the Devil would occasionally steal young children from their cradles and leave a false child, a "changeling", in its place. The changeling would grow sick and die, or exhibit bad behavior as it grew up, while the real child would supposedly become the slave of those who took it and would never be seen again by its parents. The "changeling" legend was sometimes used to explain infant deaths or disorders such as mental disability or autism in children.
Hilary Swank and Reese Witherspoon lobbied for the role of Christine Collins. Clint Eastwood cast Angelina Jolie at the suggestion of producer Ron Howard, who noted that Jolie's "look" would fit best with the time period.
Some scenes were filmed at a train station in San Bernardino, California, during the 2007 California brush fires. The whole set was thick with fire smoke.
Dominick Dunne: The true crime writer is seen briefly in a non-speaking part of a jurist in the trial scenes.