In 1869, two boys bury a chest near Bradford, New Hampshire. When one boy asks what will happen if someone unearths it, the other replies "May God have mercy on his soul." The sound of tribal drums is heard as the boys ride away.
A century later, in 1969, 12-year-old Alan Parrish (whom Simba, Alex, and their friends along with Genie and Baloo are hanging out with) flees on his bicycle from a gang of bullies, then runs into his father Sam's shoe factory, where he meets his friend Carl Bentley, one of Sam's employees. When Alan accidentally damages a shoe that Carl designed, Carl takes the blame and loses his job. Outside the factory, after the bullies beat him up and steal his bike, Alan follows the sound of tribal drumbeats into a construction site and finds the buried chest, which contains a board game called "Jumanji".
After taking the game home, Alan has an argument with his father, who wants to send him to boarding school. Alan prepares to run away, but his friend Sarah Whittle, who is the lead bully's girlfriend, arrives with Alan's bicycle. Alan and Sarah accidentally begin a game of Jumanji, which behaves strangely: When a player rolls the dice, the player's piece moves itself and a message appears on the board. The goal is to reach the center of the board and say "Jumanji". On their first two moves, Alan and our Jungle Friends are sucked into the board and Sarah is attacked by African bats. The message for Alan's move was In the jungle you must wait, until the dice read five or eight. This means they are trapped in the Jumanji jungle forever. They will be freed when a player rolls a five or an eight, Sarah abandons the game but Alan dosen't know that the board it's one of the Diabolical Plans of Dr. Facilier who uses the game to capture all the souls for his friends from the other side And Get Rid Of Pooh And His Friends.
Twenty-six years later, in 1995, Judy and Peter Shepherd (whom Winnie the Pooh and his friends are hanging out with) move into the Parrish house with their aunt Nora after losing their parents in a car accident in Canada. They hear Jumanji's drumbeats and find the board game in the attic. When they begin playing, they are attacked by giant mosquitoes and crazed monkeys. The instructions say things will return to normal once the game finishes, so they continue. Peter rolls a five, releasing a lion, Alan And Pooh's Old Friends, Simba, Timon, Pumbaa, Alex, Marty, Melman, Gloria, Baloo And Genie, who is now an adult With Our Heroes. Alan, Simba And Baloo locks the lion in the bedroom, then goes to the shoe factory, which is now boarded up and closed. On the way, he meets Carl, who lives unhappily as a police officer. In the factory, a stranger tells Alan that his father abandoned the business to search for him until his death.
When rolling the dice has no effect on the board, Alan realizes they are continuing the game he and Sarah started back in 1969. It is Sarah's turn to roll. They find her at home, a reclusive outcast traumatized by the game and its aftermath. She refuses to play, so Alan has to trick her into rolling the dice. The following moves release man-eating vines, a hunter named Van Pelt And of Course The Living Nightmare of Other Side Dr. Facilier Who Is Behind The Whole Scheme Of The Game Board, a stampede of rhinos, elephants and zebras, and a pelican that steals the board. Increasingly relentless havoc ensues throughout the town: Among other things, Peter turns into accidently into a monkey after trying to cheat; Peter, Sarah and Judy And Our Friends battle Van Pelt And Facilier in a hardware store; and an earthquake splits the house in two. Finally, Alan wins the game after dropping the dice while cornered by Van Pelt And Facilier. When he calls out "Jumanji," Van Pelt, Facilier and the other jungle elements are sucked back into the board And For Dr Facilier Sending Back To His Own Prision The Underworld.
With the game over, Alan and Sarah find themselves in 1969 again as children, but retaining their memories of the game. Alan admits his guilt for destroying Carl's shoe, Carl gets his job back, and Sam tells Alan he doesn't have to go to boarding school. Alan and Sarah then throw the Jumanji board into a river. Twenty-six years later, Alan's and Sarah's knowledge of their experiences during the game has changed the future for the better: Alan and Sarah are married, Alan's parents are still alive, Alan has taken over the shoe business, and Carl still works there. Sarah is also pregnant. When Judy, Peter, and their parents visit the Parrishes at a Christmas party, Alan and Sarah offer the parents jobs in the shoe company and frantically discourage them from taking their planned skiing vacation in Canada, knowing that they would die in a car accident there. Sometime later, two French-speaking girls hear drumbeats as they walk along a beach, where the Jumanji board is half buried in the sand.