Although he earned a degree in political science and a U. S. history teaching credential, Breen was hooked on cartooning as a career after one of his cartoons was published in Newsweek when he was only 19 years old. He won the John Locher and Charles M. Schulz cartooning awards for his work on the student newspaper at the University of California at Riverside. Breen has been an editorial cartoonist at The San Diego Union-Tribune Since July 2001. Prior to that he was at New Jersey's Asbury Park Press. He is the winner of the 2007 Berryman Award presented by the National Press Foundation.