He attended Meadowbrook Middle School and Rancho Bernardo High School in San Diego, California. According to Tony Gwynn, lots of scouts were interested in Hamels while he was pitching for RBHS because his fastball was clocked as high as 94 mph. However, he broke his arm in his junior year, so some teams, like the San Diego Padres lost interest. Nonetheless, Hamels was drafted in the first round of the 2002 Major League Baseball Draft by the Phillies.