Choi led the marathon at the 1948 Summer Olympics in London before dropping out with less than 5 kilometers left in the race. He finished third in the 1950 Boston Marathon, but the Boston Athletic Association denied his entry into the following year's event. During the height of the Korean War, BAA President Walter A. Brown stated: "While American soldiers are fighting and dying in Korea, every Korean should be fighting to protect his country instead of training for marathons. As long as the war continues there, we positively will not accept Korean entries for our race on April 19." In 1952, Choi finished fourth in the Olympic marathon at Helsinki.