An elderly widower named Carl Fredricksen, who worked as a balloon salesman, is facing pressure from the expanding urban environment to sell his house. Carl had shared a lifelong dream with his late wife Ellie to travel to Paradise Falls in South America, inspired by their childhood hero, explorer Charles F. Muntz. After an incident results in a court order for him to move to a retirement home, Carl decides to fulfill his promise to Ellie. He rigs thousands of balloons to his house, intent on flying to the remote falls. His plan is inadvertently interrupted by Russell, an earnest and talkative Wilderness Explorer Scout who was on Carl’s porch seeking to earn his final badge for assisting the elderly.

As Carl’s house takes flight, he is dismayed to discover Russell aboard. Bound for Paradise Falls, the unlikely pair embark on an adventure, navigating through stormy skies and adjusting to each other's company. The journey becomes fraught with challenges, including navigating rough weather and dealing with Carl’s grumpiness and grief. During their flight, they encounter a rare bird that Russell names “Kevin” and a talking dog named Dug, who reveals insights about Muntz's current endeavors. As they near their destination, Carl must decide between clinging to the memories of his past or embracing the new relationships and adventures that await with his unexpected companions.