Troodon are very intelligent dinosaurs. They are around 2.4 meters (8 ft) long, 1 meter (3 ft) tall, and weighed 50 kilograms (130 lb). Troodon had very long, slender limbs, suggesting that the animal was able to move quickly. It had long arms that folded against the wall of the thorax like a bird's.

It had large, retractable sickle-shaped claws on its second toes, which were raised off the ground when running.