Kahanamoku was unfazed by the controversy over his record-breaking performances in the 1911 AAU event. Instead, he focused on making the U.S. Olympic Men's Swimming Team, set to compete in Stockholm for the 1912 Games. In a May 1912 qualifying meet in Philadelphia for the 100-meter freestyle event, Kahanamoku swept the field with a time of 60 seconds. He also qualified for the U.S. 800-meter relay team at a trial held in New Jersey, where he set a record for his leg of the race with a 200-meter time of 2 minutes and 40 seconds. At the 1912 Olympic Games Kahanamoku became one of the event's most famous athletes. On July 6 he took the gold medal in the 100-meter freestyle event and set a new Olympic record in the process of 63.4 seconds. Kahanamoku also helped the U.S. 800-meter freestyle team take the silver medal in that event. Perhaps the only other American athlete to emerge with a higher profile from the 1912 Olympic Games was Jim Thorpe, who, like Kahanamoku, was of aboriginal descent.
The First World War led to the cancellation of the 1916 Olympic Games, where Kahanamoku was a favorite to win at least one more gold medal. Forced to wait until the 1920 Olympic Games in Antwerp, Belgium, Kahanamoku once again made the U.S. Team in the 100-meter freestyle and 800-meter freestyle relay. The first run of the finals for the 100-meter freestyle was nullified after some countries protested the outcome, which had thirty-year-old Kahanamoku setting another world-record of 61.4 seconds. In the rescheduled finals, he again proved his mastery of the event with an even better time of 60.4 seconds. This time, there was no protest and Kahanamoku was awarded the gold medal. He also helped to set a record as part of the 800-meter freestyle relay team, which took the gold medal with a record-setting time of 10 minutes and 4.4 seconds.
Kahanamoku's final Olympic medal came at the 1924 Games in Paris, where he placed second to Johnny Weissmuller in the 100-meter freestyle event. Kahanamoku did not make the swim team for the 1932 Olympics in Los Angeles, but he did attend the event as a member of the Los Angeles Athletic Club Water Polo Team, which failed to make it into the final competition. In all, Kahanamoku won three individual and two team medals in his Olympic career.