The genus name Scutellosaurus, means "little-shielded lizard", and is derived from the Latin word "scutelum" meaning "little shield", and the Greek word "sauros" (σαύρα) meaning "lizard". The type and only valid specie known today is Scutellosaurus lawleri. The specific name honors David Lawler who collected the fossil.
Scutellosaurus was lightly built, and was probably capable of walking on its hind legs. It had an unusually long tail, possibly to provide a counterbalance against the weight of the armored body, and long arms that suggest it may have browsed on all fours. It was around 1.2 metres (3.9 ft) long, 50 centimetres (20 in) tall at the hips, and weighed 10 kilograms (22 lb). The fossil evidence includes two partial skeletons recovered from Arizona, although of the skull only the lower jaw has been recovered. There were also several hundred scutes running along its neck to its back and as far down as its tail. These formed parallel rows, with as many as five rows on each side. It also had double rows of scutes, or external plates, running neck to tail. Some of these shields were flat, while others were pitted.