Tulio is tall and slender with blue eyes. He has long, wavy black hair, tied back with a purple ribbon in a low ponytail, and a goatee. He wears a blue collared long-sleeved shirt under a brown vest, green pants with a brown belt, and brown shoes. He appears to be in his mid-20s to early 30s.
Tulio tends to be the more strategic, logical, and level-headed of the two protagonists. He takes a romantic interest with Chel. He is initially more interested in wealth and fame than adventure (a conflicting trait with Miguel), but has a good heart: In the end, he is willing enough to give up his gold in order to protect the citizens of El Dorado from Hernán Cortés's army.
In times of trouble, Tulio is usually the one who comes up with a clever plan. He tries his best to remain realistic in every situation in order to stay out of trouble. A quick thinker, he is able to use words and improvisational acting to his advantage (like Miguel), and although he and Miguel have opposite personalities, values and ideas, the two deeply care about each other, and are unable to stay mad at each other for long without feeling guilty. Even Tulio is easily approached by Chel's beauty (see Chel). Still, even though Chel is Tulio's sweetheart, he never forgets his camaraderie with Miguel.
- He is shown to hook up with Chel, though there is a big gap in age range. He even states how he was alive before she was born.
- However, it is worth noting that age gaps of similar, or greater, size were relatively common in Tulio and Chel's time.