Fitzgibbon won the singles title at the tournament in Cincinnati, Ohio in 1964 and was a two-time singles runner-up (1965 and 1963) there as well. He also reached the Cincinnati doubles final with Butch Newman in 1965. That year, he also won the Long Island Championships and the Eastern Clay Court title. In 1968, Fitzgibbon won against 16th-seeded Nikola Pilić in the first round at Wimbledon, 3–6, 7–5, 6–3, 6–2. The same year he won the La Coruna International in Spain against Juan Gisbert Sr..
