The prehistoric Croods family live in a particularly dangerous moment in time. Patriarch Grug, his mate Ugga, teenage daughter Eep, son Thunk, and feisty Gran gather food by day and huddle together in a cave at night. When a more evolved caveman named Guy arrives on the scene, Grug is distrustful, but it soon becomes apparent that Guy is correct about the impending destruction of their world.

As the son of a Viking leader on the cusp of manhood, shy Hiccup Horrendous Haddock III faces a rite of passage: he must kill a dragon to prove his warrior mettle. But after downing a feared dragon, he realizes that he no longer wants to destroy it, and instead befriends the beast – which he names Toothless – much to the chagrin of his warrior father.

With the impending ice age almost upon them, a mismatched trio of prehistoric critters – Manny the woolly mammoth, Diego the saber-toothed tiger and Sid the giant sloth – find an orphaned infant and decide to return it to its human parents. Along the way, the unlikely allies become friends but, when enemies attack, their quest takes on far nobler aims.