At the 1956 Melbourne Olympics, John Tynan was a member of the New Zealand field hockey team that placed sixth overall at the tournament; Tynan appeared in at least four of the squad’s six matches. This was the most notable moment of his international field hockey career, although he was a member of the New Zealand national team for many years, from 1948 through 1956. He was also active a cricketer with the Wellington team, playing four first-class cricket matches with them between 1952 and 1954.