The title of the film is "Goodbye Christopher Robin" and it's about the difficult relationship between Milne and his son Robin, who inspired the character of Christopher and whose teddy bears provided the names for Winnie, Tigger, Piglet and Eyeore, reported Deadline.
"Star Wars" and "The Revenant" actor Domhnall Gleeson is to play Milne, while his About Time co-star Margot Robbie - also of the upcoming "Suicide Squad" - will portray his wife Daphne.
Director Simon Curtis is behind the camera. "24 Hour Party People" screenwriter Frank Cottrell Boyce and Simon Vaughan - who worked on 2004's TV movie "A Bear Called Winnie"- have written the script.
Director Curtis said: "I am delighted to be collaborating with Frank Cottrell Boyce to tell the remarkable and poignant story of the family behind the creation of Winnie the Pooh.
"We are assembling a wonderful cast, headed by two actors I am longing to work with - Domhnall Gleeson and Margot Robbie.