At the 2012 United States Olympic Trials, the qualifying meet for the 2012 Summer Olympics, Eaton started day one of the decathlon competition with two world decathlon bests, the equivalent of a world record for athletes competing in a full decathlon. The first in the 100-meter (10.21), and then in the long jump (). To emphasize the quality of Eaton's first two marks, the 100-meter time equaled the minimum (season wide) time required for men to qualify for the trials 100-meter race and only .03 short of the Olympic "A" standard. The long jump was farther than the top qualifier in the long jump preliminary round held that same day at the trials, beyond the "A" standard, and would have tied for second in the final. He went on to finish fifth in the shot put (), first in the high jump (), and first in the 400 m (46.70) held in a pouring rainstorm. After day one, Eaton's points total of 4728 was more than 300 points ahead of second-place competitor Trey Hardee. On the second day of competition, Eaton finished first in the 110-meter hurdles with a time of 13.70. In the discus, however, he had an eighth-place finish. He bounced back in the pole vault, posting a height of , good enough for first place. In the javelin throw, Eaton had a distance of for fifth place. Going into the final event, the 1500 m run, Eaton held a 317-point lead over his closest competitor, Hardee. Eaton ran a new personal best in the 1500 m with a time of 4:14.48, finishing first. In the process, he brought his total score for the decathlon to 9039, breaking Roman Šebrle's previous world record of 9026 points. Eaton broke Dan O'Brien's American record of 8891 points set in 1992.