This film appeared not long after the film Truman Capote - A sangue freddo (2005). While Infamous goes deeper into the background of the killers, Capote focuses intensely on the relationship between Capote and Smith. As such, the two films could be considered to be companion pieces.
Mark Wahlberg was originally attached to play Perry Smith, but dropped out in August 2004. He was replaced in October 2004 by Mark Ruffalo, until he dropped out as well.
This film was overshadowed by the film Capote that featured Phillip Seymour Hoffman as Truman Capote. It was released just prior to this one. Coincidentally, Toby Jones, who plays Capote here, played Alfred Hitchcock in an HBO movie that was again overshadowed by a theatrical film released around the same time featuring Anthony Hopkins as Hitchcock.
This film and Truman Capote - A sangue freddo (2005) were written and produced almost simultaneously but Bennett Miller's film got released first and received several accolades during the awards season.
Douglas McGrath heard a story about the real Diane Vreeland making her maid iron the money. He liked that so much that he included it in the movie.