Reto Delnon played ice hockey in the Swiss leagues for more than two decades with only a brief break for the 1949–50 season when he played for HC Milano in Italy. Delnon played in 79 matches for the Swiss national team where he won three bronze medals at the World Ice Hockey Championships (1939, 1950, 1951). The European Ice Hockey Championships were contested as part of the World Championships, with his bronze medals at the latter in 1939 and 1951 equating to gold at the European Championships. In 1952 he was also part of the Swiss team that competed at the Oslo Olympics. Delnon retired in 1964 and became a coach and club President at HC La Chaux-de-Fonds. In the early 1960s he served a very brief spell as the coach of the national team but was forced to resign after it emerged he was a member of the Communist Party of Labour.