Christopher Robin is moving to a boarding school in London so his stuffed animal friends from the Hundred Acre Wood, consisting of Winnie the Pooh, Tigger, Piglet, Eeyore, Kanga, Roo, Owl, and Rabbit throw him a going away party. Nearing the time of his departure, he tells Pooh that he won't ever forget him. However, due to the constant teasing he receives from other school boys and the teacher's strictness, he soon loses all sense of imagination and matures.
In present day, Christopher is now a full-grown adult, working as an efficiency expert at a luggage company, managed by the demanding Giles Winslow Jr. He is also married to an architect named Evelyn and has a daughter named Madeline, whom he plans on sending to the same boarding school he was sent to as a kid. Due to other counties in England having seeing their services as unnecessary, Giles tells Christopher that they must lay off 20% of the employees and Christopher must do paperwork on it and turn it in by Monday, despite the fact that Christopher has planned a weekend getaway to the countryside with his wife and daughter. After telling Evelyn about the task at hand, she tells Christopher that his life is happening before him and he must see it and she and Madeline head out into the country the following morning.
Meanwhile, in the Hundred Acre Wood, Pooh awakens to see that he has run out of honey and discovers that the Wood has been deserted. Believing Christopher Robin knows what to do, he is suddenly confronted with a magical door that leads to the real world and goes through it and ends up in London, where the overwhelming tribulations he goes through tire him out, so he rests on a bench in an unknown garden. Coincidentally, Christopher sits on the bench behind it in the same garden while trying to figure out how to do his work and in an instant, the two are reunited. Christopher is shocked to see Pooh after so many years and soon reluctantly agrees to take Pooh back to the countryside since the doorway he came in magically vanishes. After many misadventures in the city, the two hop on a train headed for the countryside while Christopher tries to do his paperwork.
Christopher tries to leave Pooh at the tree to go back to the Hundred Acre Wood but eventually decides to reluctantly help Pooh find his friends in the Hundred Acre Wood. After searching for hours, Christopher eventually becomes exasperated at Pooh's absent-minded childishness when they come across a sign that gives a warning about Heffalumps and Woozles, to which Christopher scoffs at due to them being non-existent, but soon feels guilty about yelling at Pooh when the two are separated. Christopher soon finds Eeyore and Piglet and eventually discovers that everyone in the Hundred Acre Wood, Tigger, Rabbit, Owl, Kanga, and Roo are hiding in a tree because they think they hear a Heffalump in the area. Christoper decides to pretend to fight off the Heffalump so that his friends can come out of hiding. After a short reunion, Christopher leaves the woods after finishing his paperwork and his friends are sad that he has left after a short while. Christopher encounters his wife and daughter when they see him from the cottage he used to live in as a boy and they believe that he has decided to be with them after all, but they are disappointed when he explains that he really must get to Winslow and is unable to explain why he is in the countryside.
In the Wood, Pooh, Piglet, Eeyore, and Tigger find Christopher's paperwork, or as they call it his 'Important Things', and they decide to go to London and return it to Christopher since they believe a 'Woozle' (actually Winslow) will eat him if he doesn't turn them in. En route, they encounter Madeline, who recognizes them as a drawing made by Christopher when he was young. She feels as though if she helps them return Chirstopher's paperwork, he will reconsider sending her to boarding school. She leaves a note for Evelyn and takes the stuffed animals to London. Christopher arrives at the luggage company to promote his idea to cut 20% of the work force to Giles and his father, Giles Winslow Sr., but soon discovers that his paperwork is missing. As he tries to save face for the Winslow's, Evelyn comes in and shows him Madeline's note, leading the two to go find and Christopher knows she's with Pooh and his friends based on the word 'expotition'. Meanwhile, after they reach London, Madeline and the stuffed animals see that they're running out of time to get to Christopher's meeting, so Tigger, Piglet, and Eeyore ride on a suitcase tied to a car to get there and eventually land on Christopher and Evelyn's car, but they lose his paperwork in the process. Meanwhile, Pooh and Madeline make it to Wisnlow's Luggage and find the paperwork, but a gust of wind blows it away.
Christopher and Madeline reunite and he promises to be a better father and says that she doesn't have to go to boarding school, now seeing that his family is more relevant then his job. An off-hand comment from Evelyn gives Christopher an idea on how to save the company and he goes back to Winslow's office to propose his idea, to do nothing as he believes people who go on vacations will buy their luggage and humiliates the stuffy Winslow by calling him a 'Woozle' since he hypocritically takes time away from work himself to go golfing. Impressed and amused at this, Winslow Sr. agrees to Christopher's idea and decides not to lay off his employees. The film ends with Christopher and his family having their retreat to the countryside as they visit the Hundred Acre Wood, meeting all of Christopher's stuffed animal friends.