Donatello is a mutant spiny softshell turtle with jade green skin, a light brown plastron, and a brown and green carapace with dark brown spots. The vertebrae of his spine protrude from underneath his carapace and he has geometric purple markings on his shoulders and thighs. He also has a large head, yellow sclerae and teeth, thick black eyebrows, three fingers on each hand, and two toes on each foot. He wears a purple bandana that covers the top of his head with short rectangular bandana tails.

Aged up to 18