The 35-year-old actress is set to play Monroe in an adaptation of Andrew O'Hagan's 'The Life And Opinions Of Maf The Dog, And Of His Friend Marilyn Monroe', reported Daily Mail online.
Clooney has been lined up to play Monroe's close friend Sinatra, O'Hagan confirmed, adding that production on the film would begin soon.
While Scarlett Johansson and Christina Hendricks had previously been in line for the role, it was eventually decided Jolie would be the best choice to play Monroe in the new film.
O'Hagan's novel tells the story of Monroe's final two years before her death in 1962 through the eyes of her pet Maltese terrier Maf, a gift from 'My Way' singer Sinatra in 1960.
As well as meeting Monroe's friends including former US President John F. Kennedy, Maf also accompanied the star to acting classes and restaurants.
When she received the dog from Sinatra, Monroe decided to call it Mafia, a joke reference to Sinatra, before shortening the name to Maf, or Maf Honey.
When Monroe died in August 1962 aged 36, Maf was inherited by Sinatra's secretary Gloria Lovell.