Milne was an early screenwriter for the nascent British film industry, writing four stories filmed in 1920 for the company Minerva Films (founded in 1920 by the actor Leslie Howard and his friend and story editor Adrian Brunel).
Milne is most famous for his two Pooh books about a boy named Christopher Robin after his son, Christopher Robin Milne, and various characters inspired by his son's stuffed animals, most notably the bear named Winnie-the-Pooh.