Camptosaurus is closely related to Dryosaurus. It had small, hoof-like claws on both its fingers and toes, indicating that it frequently walked on all fours.

Both young and adult Camptosaurus skeletons have been found, ranging from juveniles the size of a German Shepherd to adults at a full-grown 23 feet. An early iguanodontian, Camptosaurus is smaller than its later relative Iguanodon. Other differences include its four toes (compared to Iguanodon's three) and the underdeveloped spike on its thumb.

Camptosaurus is known from the western United States and from England, providing evidence for a land connection between these two regions during the latter part of the Jurassic Period. By the Early Cretaceous, the continents had begun to separate, causing animals on each landmass to evolve independently.