Leonardo is the oldest of the four brothers, and the one with the calmest demeanor. He usually takes charge of the four, but doesn't usually directly refer to himself as the leader. He weilds dual katanas, and is alluded to read more often than his other brothers. In later renditions, Leonardo is constantly serious, rarely making jokes, and displaying excellent leadership skills.

Voiced by James Arnold Taylor in the 2007 movie. He is voiced by Nolan North in the video game 'Teenage Mutant Ninja Turtles: Mutants in Manhattan'.