He is described as "about a million years old, with bifocals and no teeth and a greasy wave of gray hair". He appears in the second book, The Sea of Monsters, when Percy and his cyclops brother Tyson are in a dodgeball game against Percy's bully, Matt Sloan, and six Laistrygonian giants in Meriwether College Prep.
Percy was in his gym class while playing an innocent dodgeball game with his brother Tyson when they were attacked by Laistrygonian giants. Coach Nunley generally pays little or no attention to what is happening in gym class whether that's bullying or monsters, preferring to keep his nose buried in a copy of Sports Illustrated magazine. He also wears hearing aids. When he answers any of the students' questions, it is always "Un- huh." or "Go ahead." This leads to Percy getting blamed for all the destruction caused by the Laistrygonian Giants during the "dodgeball" game. This event resulted in Percy not being allowed to enroll in the school the following year. This also placed Percy in the newspapers. He was wanted for the explosion until Chiron manipulated the Mist.
- Percy says that Coach Nunley reminds him of the Oracle except for the fact that he does not billow green smoke.