After starting out as a rower, George Breen first took up swimming seriously at the relatively late age of 17, but he went on to win 22 AAU championships and set six world records. His greatest performance came at the 1956 Olympics, where he lowered the world 1,500 freestyle record by 13 seconds. Unfortunately this was in the heats and he could not repeat this form in the final, where he finished third. At the 1959 Pan American Games he won gold in the 400 free and silver in the 1,500 free, and then repeated as bronze medalist in the 1,500 at Roma in 1960. Breen attended Cortland State University and later did graduate work at Indiana.
Breen later became the head swim coach at Penn from 1966-82. He also coached club swimming in New Jersey with the Jersey Wahoos and at the Gloucester County Institute of Technology. He was active in swimming administration, serving as chair of USA Swimming Olympic International Operations Committee, and was a long-time member of Middle Atlantic Swimming’s Board of Directors, as well as a member of the USA Swimming Board of Directors. Breen was inducted into the International Swim Hall of Fame, the American Coaches Association Hall of Fame, and the Cortland State Hall of Fame.