He competed for the Oregon Track Club Elite team based in Eugene, Oregon. In college, Eaton competed for the University of Oregon, where he was a five-time NCAA champion, and won The Bowerman award in 2010. In 2011, Eaton won the first international medal of his career, a silver, in the decathlon at the 2011 World Championships. The following year, Eaton broke his own world record in the heptathlon at the 2012 World Indoor Championships, and then broke the world record in the decathlon at the Olympic Trials. After setting the world record, Eaton won the gold medal at the 2012 Summer Olympics in London. He successfully defended his Olympic title in Rio 2016 by winning the decathlon gold medal and tying the Olympic record. Eaton is only the third Olympian (after Bob Mathias of the US and Great Britain's Daley Thompson) to achieve back-to-back gold medals in the decathlon.