In March 1951, Iwatani was selected Japan national team for Japan team first game after World War II, 1951 Asian Games. At this competition, on March 7, he debuted against Iran. On march 9, at 3rd place match, he scored 2 goals against Afghanistan and Japan won the match 2-0. He also played at 1954 Asian Games. In June 1956, at 1956 Summer Olympics qualification, he played as captain against South Korea and Japan finished with one win and one defeat. After the qualifiers, he takes part in drawing of lots as captain and got won the qualification to 1956 Summer Olympics. However, in November, he was not selected Japan team for Olympics. He played 8 games and scored 4 goals for Japan until 1956.