Between 1953 and 1973 Cahill made 72 senior appearances for Ireland. He made his debut for Ireland in February 1953. He helped Ireland win the 1968 Home Nations Championship, the 1972 Santander Trophy and toured South Africa in 1973. He also represented Ireland at the 1970 Men's EuroHockey Nations Championship. On 29 April 1973, Cahill made his final appearance for Ireland against Belgium. In 2006 Cahill was inducted into the inaugural Irish Hockey Association Hall of Fame. Other inductees included David Judge, Maeve Kyle and Thelma Hopkins.