Hanno Selg started out as a skier and won his first medals at the Estonian SSR championships, a silver in 4x10 km relay and a bronze in slalom in 1952. In 1953, Selg took up modern pentathlon and between 1953-65, Selg won six Estonian SSR modern pentathlon titles, one winter pentathlon title and one individual fencing title. In 1960, Selg won his only Soviet title and was selected to the Soviet 1960 Olympic team. At the Olympics, which were his only international tournament, Selg won silver in the team competition and was 10th individually. In 1960, Selg was also selected as the best Estonian athlete of the year. After finishing his sporting career in 1965, Selg worked as a modern pentathlon coach and judge until 1979. From 1979-94 Selg worked as a professor at Tartu University and since 1995 has owned a private bus operating company, servicing local lines around Tartu.