The nasal horn of Einiosaurus was unique, being flattened from side-to-side and with a tip that curved over the end of the snout. In young animals, the horn was short and erect, and as the animals matured, it curved forwards. Like most other members of the Centrosaurine group, Einiosaurus lacked brow horns and had either small lumps or rounded pits in their place. The margins of its frill were wavy, and two long spikes projected upwards from the frill is upper border. This spikes were straight, and it is difficult to imagine how they might have functioned in combat.