Plateosaurus was among the earliest dinosaurs to attain a relatively large size, growing to about 8 metres (26 feet) long. It was more massive than earlier dinosaurs and had bones that were stocky and thick. Although Plateosaurus could rise up on its two very strong hind legs, its forelimbs also were relatively well developed and strong, and it may have walked on two or four legs for various purposes. The small skull was perched atop a long, flexible neck and contained flat teeth serrated on the front and back edges.

Plateosaurs were the first known large herbivores among the dinosaurs. Dinosaurs related to Plateosaurus have been found in South Africa, North America, and China. The prosauropod group of dinosaurs is not found after the Early Jurassic Period (200 million to 176 million years ago), which is when the first of the large “true” sauropod dinosaurs appeared. This fact, along with the increasing trend to large size among prosauropods, supports the idea that sauropods evolved directly from prosauropods, although some authorities regard the two as separate groups.