Nobita finds a fossilized dinosaur egg by accident, and with the help of Doraemon's tools, the egg hatches and begins growing into a dinosaur. Knowing that they can't keep the dinosaur forever, Nobita is forced to send it back to prehistoric times where a group of hunters from the future threatens to endanger the dinosaurs. Determined to save the dinosaurs from the claws of the hunters, Doraemon and the gang returns to the past and set out on a prehistoric adventure.