Percy Jackson is 12 years old in the first book, Percy Jackson and the Olympians: The Lightning Thief.

Quick Scoop

  • In The Lightning Thief , Percy introduces himself as a 12‑year‑old sixth grader at Yancy Academy.
  • Multiple fan and book-focused sites confirm that Percy is 12 years old during the events of the first book.
  • Across the original series, he ages from 12 in the first book up to 16 by the final installment, but he starts his journey at age 12.

Information gathered from public forums or data available on the internet and portrayed here.