Three years have passed since the last adventure, and now Spencer, Fridge, Martha, and Bethany have gone their separate ways, although they plan to reunite in Brantford. However, Spencer is feeling anxious about their meeting, particularly with Martha, whom he has put on hold due to his belief that they might have better lives apart. On the first night back, it becomes clear to him that his experiences in Jumanji are what truly made him feel alive, prompting him to seek a way back into the game.
The following day, when Spencer doesn’t show up, his friends grow increasingly concerned. They visit his home and meet his grandfather, [Eddie](danny-devito) (staying there while recovering from hip surgery), along with his old friend [Milo](danny-glover) (who is visiting). It’s during this encounter that they discover Spencer has kept the broken pieces of the Jumanji game. Determined to rescue him, the group decides to re-enter the game, but it malfunctions and only pulls in Fridge, Martha, Eddie, and Milo, leaving Bethany to seek help from fellow Jumanji player [Alex](nick-jonas).
Inside Jumanji, Martha takes on the role of Ruby Roundhouse ([Karen Gillan](karen-gillan)), a skilled commando who can wield Nunchucks but is still vulnerable to venom. Meanwhile, Fridge becomes Professor Oberon ([Jack Black](jack-black)), transitioning from Bethany's previous character, and Eddie and Milo find themselves as Bravestone ([Dwayne Johnson](dwayne-johnson)) and Mouse ([Kevin Hart](kevin-hart)), respectively. After a harrowing encounter with a python leads to Fridge losing a life, the group learns about a new threat: a warlord named Jurgen the Brutal. This villain poses a grave danger to Jumanji, having stolen a magical necklace—the Falcon's Heart—which is crucial for sustaining the land. The group must reclaim it before Jurgen sells it to a criminal organization, as this is the key to ending an ongoing drought plaguing their world.
As they venture into the desert known as the Dunes, every character uncovers new strengths and weaknesses. A narrow escape from a flock of ostriches costs Eddie his first life, and they find an oasis where they reluctantly reunite with Spencer, who is now inhabiting a new character: Ming Fleetfoot ([Awkwafina](awkwafina)), a thief with potential but also a significant weakness. Throughout their journey, the group faces numerous challenges, including confrontations with Jurgen's men and navigating misunderstandings and conflicts within the group.
Key setbacks and mishaps—like Milo’s untimely demise due to a boulder and Martha losing a life to mandrills—bring the team closer to their last chances. Luckily, they eventually find a magical river that allows them to revert to their original avatars. Just when things seem to be turning around, the group falls into the clutches of Jurgen's fortress. In a climactic showdown, Spencer fights Jurgen, using the Jumanji Berry to thwart the warlord’s advances. With the team’s collaboration, they manage to reclaim the Falcon's Heart and expose it to sunlight just in time to save Jumanji.
Returning to the real world, Spencer takes a moment to reconnect with his grandfather by sharing his passion for video games. They also encounter [Nora Shepperd](bebe-neuwirth), the new owner of Eddie's diner, where the group plans to reunite. The mid-credits scene reveals a mechanic, hired by Spencer’s mom, who inadvertently triggers the game once more, setting up a new adventure as a flock of ostriches escapes into the real world.
