Diego is an 8-year-old Latino action-adventure hero with a big heart. His goal is to save and protect the animals and their environment. Athletic and fearless, he is always at the ready no matter what the situation. Diego loves learning new things he as a merboy. He takes a scientific approach to problem solving and also uses a variety of high-tech gadgets and gizmos to save the day. Diego learns a lot from his parents who are proud that their son cares for nature. In Diego Saves Baby River Dolphin! and Tuga Helps the Moon, it is shown that Diego is very ticklish. As shown in Diego Saves Baby River Dolphin!, Diego finds river dolphin beaks very tickly, as Baby River Dolphin rubbed his beak on Diego's chin and Diego thinks it tickles. Diego is the youngest child in the Marquez family and the only son to his parents.
He's voiced by Jake T. Austin Seasons 1-3; Matt Hunter Seasons 4-5.