Demaria was a dual internationalist, playing for Argentina from 1930-31 (13 appearances, 3 goals), including the first World Cup in 1930, where Argentina finished as runner-up to Uruguay.
He played for Italy from 1932-40 (3 appearances, no goals), including the 1934 World Cup, which Italy won to claim their first World Cup title.
He died on 11 November 1990 at the age of 71 in Haedo, Argentina.