At the 1920 Summer Olympics he won the silver medal in the decathlon, losing to the Norwegian Helge Løvland by only four points, and finished sixth in the pentathlon.

[1] After the 1924 Olympics, Hamilton coached track and field at Westminster College in Fulton, Missouri, where he also instructed students in English and history.

He coached at Cal from then until his retirement in 1965, with time off to serve as a major in the U.S. Air Intelligence in England during World War II.

He was athletic director at Berkeley from 1946 to 1955, during which time he recruited both Lynn (Pappy) Waldorf and Pete Newell, two of Cal's greatest coaches; he was an assistant dean of students; and he chaired the NCAA Track and Field Rules Committee for 10 years.

At Cal, Hamilton coached many athletes of great ability, among them Archie Williams, Hal Davis, Grover Klemmer, Guinn Smith, Jack Yerman, Jerry Siebert, Leamon King, Don Bowden (the first American to break the 4-minute mile barrier), Lon Spurrier, Willie White, Dave Archibald, Forrest Beaty, and Dave Maggard.