In 1869, somewhere in Brantford, New Hampshire, brothers Caleb and Benjamin bury a box in the ground and hope that no one ever finds it. A hundred years later in 1969, Alan Parrish, a 12 year-old boy, flees from a group of bullies led by Billy Jessup and escapes to his father Sam’s shoe factory. There Carl Bentley, his friend, unveils a new shoe design which he made himself.
Adam misplaces the shoe and destroys a machine, but Carl decides to take full responsibility for the damages and get fired. Jessup’s group beat up Alan and take his bicycle, and after this happens, he begins to hear the sounds of drum beats which he follows straight to a construction site. There, he stumbles upon a box that contains a board game called Jumanji, which he takes back with him to his house.
Back at home, Alan argues with his father about attending Cliffside; a boarding school for boys. Alan has plans of running away but Sarah Whittle, his best friend, comes over to return his bicycle to him. Alan then shows Sarah Jumanji and invites her to play the game with him. Anytime the dice is rolled, the game piece moves on its own and then a metaphorical message appears in the crystal ball at the centre of the game itself.
Sarah reads the first message on the board and hears a strange sound right after. Alan then accidentally tolls the dice again after he is startled by the chiming clock. A message appears again, instructing Alan to wait in a jungle until someone rolls a 5 or an 8. Alan is immediately sucked into the game and a swarm of bats begin to chase Sarah out of Alan’s home.
In 1995, about 26 years after Alan’s incident, Judy and Peter Shepherd move into the unoccupied Parrish mansion with their Aunt Nora after their parents die in an accident on a Ski trip. Much later, Peter and Judy find Jumanji and start to play the game. When they roll the dice, a swarm of mosquitoes are released, followed by a group of monkeys.
The game’s rules reveal to them that all things will go back to normal when the game comes to an end, so the duo keep on playing. Peter rolls the dice and this time he releases a lion, along with Alan who is now an adult. As Alan tries to leave, he stumbles upon Carl who is now a police officer. Alan, Peter and Judy head over to the now closed shoe factory where a homeless man reveals to Alan that his disappearance caused Sam to abandon his job and keep searching for Alan with his wife till he died about four years earlier.
Alan is heartbroken by the news, especially since he finally realizes that his father actually loved him more than he knew. The three realize that they will need Sarah to finish the game, they find her now suffering from post-traumatic stress disorder due to Alan’s disappearance and together, they convince her to join them.
When Sarah rolls the dice, she unleashes rapid-growing carnivorous plants and when Alan rolls the dice next, he releases a bounty hunter; Van Pelt. Judy rolls the dice next and unleashes a stampede of wild animals, during which a pelican grabs and steals the game. Peter is able to retrieve the board game but Carl arrests Alan for hijacking his car.
The group eventually return to the mansion but it is totally full of jungle animals. They try to release and dodge many dangers but Van Pelt shows up and faces off against Alan. Alan eventually drops the dice and wins the game, leading to the reversal of all events caused by the game.
The game reverses Alan and Sarah back to the time they stated playing the game in 1969 as children, but leaves them both with memories of all their adventures together in the game. Alan settles his grievances with his father and admits to being responsible for the accident at the shoe factory that destroyed the machine. Carl is re-employed and when Sam realizes that Alan is much happier being at home and with Sarah, he tells Alan that he does not have to go to boarding school.
Alan and Sarah toss Jumanji into a river and share a kiss. Fast-forwarding to 1995, Alan and Sarah are married and expecting their first child. Sam has retired (but he and his wife are still alive) and Alan is now in charge of the shoe factory, with Carl still working at the factory too. Alan and Sarah eventually meet up with Peter and Judy who have no memories of the game, at a Christmas party, they also finally meet their parents; Jim and Martha.
Peter and Sarah persuade Jim and Martha to cancel their upcoming ski trip, hence, helping them avoid their deaths and then they go on to offer Jim a job at the factory. At the end of the film, two young girls are seen walking along a beach when drum beats begin to play and Jumanji is shown lying in the sand.