Christopher Robin was with friends dressed as Pooh characters
The clip was unearthed during research for a new BBC documentary celebrating the 75th birthday of the children's books.
The 10-second piece shows Christopher Robin Milne, son of creator AA Milne, following school children dressed for a pageant as Winnie the Pooh, Piglet, Eyeore, Tigger and Kanga.
He was nine years old when the film was shot in the Ashdown Forest, East Sussex, in 1929.
Although Christopher Robin was unaware of the film he remembered the pageant and wrote about it in his autobiography
It says: "The pageant went its memorable way and I see it as an ancient cine film, much faded and blurred and with many breaks, but with here and there and a sequence as vivid as the day it was shot. It was exciting doing my bit."
Helen Kent was the BBC producer who discovered the footage, while looking for shots of the Ashdown Forest.
To her amazement the film she requested contained shots of Christopher Robin himself.
Ms Kent said: "I couldn't believe I had discovered actual footage of the real Christopher Robin Milne."
Frank Gray, director of the South East Film and Video Archive where the piece was found, said: "If anyone asked me 'would this film still exist?' I would have said 'no' as 80% of the films from the 1920's have been lost.
"This is the only film we have of Ashdown Forest from that period, so for this one film to be the film that also showed Christopher Robin was virtually impossible.
"It's a wonderful piece of film because it links the world of Winnie the Pooh to Ashdown Forest and Christopher Robin."