Espio the Chameleon is an anthropomorphic chameleon who is an expert ninja. He is also 16 years old. He is described as the "guardian of honor" of the Chaotix, also being the calmest. He has a "militaristic discipline" while also being quiet and laid back. Confident in his skills, opinionated and self-obsessed, he revels in training and self discipline. He is not concerned by danger, and often yearns to face it in order to use his ninja skills. With his extensive training in ninjutsu and an ability to turn himself invisible, he is able to move around unnoticed. However, a blunder like a sneeze could cause him to inadvertently become visible. Espio also made an appearance in Mario and Sonic at the Olympic Games as a referee.

GameZone staff writer Louis Bedigian claimed that "Espio must think he's part hedgehog because he can speed boost and become invisible".