Shozo Sasahara did not take up wrestling until he became a student at Chuo University, but he quickly demonstrated a considerable aptitude in the sport. He won his first Japanese national championship in the featherweight, freestyle category in 1953 and defended his title the following year. His next stop was the 1954 World Championships, where he captured the gold medal. Two years later he repeated these successes, winning the national championship, as well as gold at the 1956 Melbourne Olympics. He retired from active competition shortly thereafter and turned to coaching for the Japanese national team. Among his students was Osamu Watanabe, who earned gold in the same event as Sasahara at the 1964 Tokyo Games.
Sasahara was also active as an administrator in his sport, serving as President of the Japan Wrestling Association from 1989 through 2003 and Vice-President of both the Japan Olympians Association and the International Federation of Associated Wrestling Styles (now United World Wrestling) for many years. In 1995 he received the Olympic Order in Silver and in 2006 he was inducted into the International Wrestling Hall of Fame. He also invented a game known as “bound tennis”, which is tennis on a smaller court, establishing a federation for it in 1981 and serving as the first president.