On August 23, 1979, Yokoyama debuted for the Japan national team against North Korea. In 1980, he played in all matches included 1980 Summer Olympics qualification and 1982 World Cup qualification. In 1983 and 1984, he also played at 1984 Summer Olympics qualification. This qualification was his last game for Japan. He played 31 games and scored 10 goals for Japan until 1984.