In a prehistoric world, a cave-dwelling family known as the Croods have survived numerous dangers and catastrophes by sticking to the strict rules of their patriarch, Grug. The family's routine is disrupted when they encounter a more evolved, modern family named the Bettermans—Phil, Hope, and their daughter Dawn—who have built an elaborate treehouse with ingenious contraptions and lush farmlands. The Bettermans welcome the Croods with open arms, but their initial hospitality hides underlying tensions.

As the Croods experience a world of plenty and innovation, they clash with the Bettermans' sophisticated ways, leading to comedic misunderstandings and rivalry. The families struggle to coexist, with Grug growing increasingly wary of the Bettermans' intentions, especially regarding the future of his daughter Eep and her blossoming relationship with Guy, a nomadic boy accompanying the Croods. While navigating their differences, both families are soon faced with a larger threat that forces them to work together and reevaluate their perspectives on life, family, and what it means to truly evolve.