The Australian actress will star as the FBI director John Edgar Hoover's secretary of 54 years Helen Gandy, who after his death destroyed his personal file containing incriminating material that he used to control powerful political figures.
Although Naomi, 42, was studio bosses' first choice for the role, feared schedule conflicts meant Charlize Theron was considered to step in - but she instead accepted the role of the Evil Queen in 'Snow White and the Huntsman' and is also rumoured to be case in Ridley Scott's 'Prometheus'.
Dame Judi Dench is also set to star as Hoover's mother.
She revealed plans were afoot for the project, but no script had been written for her to sign up to.
She said: "It sounded like a good idea, but The Script's not there yet. I'd love to have been a Hitchcock blonde.
"A few directors I've worked with have been heavily influenced by Hitchcock, so I feel like I've gotten close."