It was reported last year that the actress would play journalist Emma Forrest in the upcoming memoir adaptation, which would reunite her with Harry Potter director David Yates.
Stanley Tucci, who is signed on to play Forrest's psychiatrist, revealed to Digital Spy that Watson is no longer attached to the project, with Emily Blunt now set to take the lead role.
It is hoped that production will begin in late spring, although Yates's departure leaves the film in search of a director. Watch the video above to find out what Tucci had to say.
Your Voice In My Head follows Forrest's experiences as a young writer in New York and her sessions with a therapist who she credits with saving her life.