Luckily for young Arlo, his parents (Jeffrey Wright, Frances McDormand) and his two siblings, the mighty dinosaurs were not wiped out 65 million years ago. When a rainstorm washes poor Arlo (Raymond Ochoa) downriver, he ends up bruised, battered and miles away from home. Good fortune shines on the frightened dino when he meets Spot (Jack Bright), a Neanderthal boy who offers his help and friendship. Together, the unlikely duo embark on an epic adventure to reunite Arlo with his beloved family.
- Raymond Ochoa as Arlo, the youngest of the Apatosaurus family
- Jack McGraw as Young Arlo
- Jack Bright as Spot, a 6–7-year-old human caveboy who befriends Arlo.
- Sam Elliott as Butch, a Tyrannosaurus who runs a "ranch" filled with prehistoric "longhorns".
- Anna Paquin as Ramsey, Butch's daughter
- A.J. Buckley as Nash, Butch's son
- Jeffrey Wright as Poppa Henry, the father of the Apatosaurus family.
- Frances McDormand as Momma Ida, the mother of the Apatosaurus family.
- Marcus Scribner as Buck, Arlo's brother
- Ryan Teeple as Young Buck
- Maleah Padilla as Libby, Arlo's sister
- Steve Zahn as Thunderclap, a pterodactyl
- Mandy Freund as Downpour, a pterodactyl who is a member of Thunderclap's flock
- Steven Clay Hunter as Coldfront, a pterodactyl who is a member of Thunderclap's flock
- Peter Sohn as Forrest Woodbush, a Styracosaurus who has various animals perched on his horns.
- Dave Boat as Bubbha, a Velociraptor rustler
- Carrie Paff as Lurleane, a Velociraptor who is a member of Bubbha's pack.
- John Ratzenberger as Earl, a Velociraptor who is a member of Bubbha's pack.
- Calum Mackenzie Grant as Pervis, a Velociraptor who is a member of Bubbha's pack.