In August 2008, Okazaki was selected the Japan U-23 national team at 2008 Summer Olympics and played all 3 matches. On October 9, 2008, he debuted for the Japan national team against United Arab Emirates. After the debut, he played many matches as forward or offensive midfielder. He was selected the japan for 2010 World Cup. However he lost his position just before 2010 World Cup and he played as substitute in all 4 matches. After the 2010 World Cup, he became a regular player again under new Alberto Zaccheroni. In 2011, he participated 2011 Asian Cup. He played all 6 matches and scored 3 goals, and Japan won the champions. In 2013, he participated 2013 Confederations Cup. He played all 3 matches and scored 2 goal against Italy and Mexico. In 2014, he was selected the Japan for 2014 World Cup. He played all 3 matches and scored a goal against Colombia. His opportunity to play decreased from 2017. He also played at 2018 World Cup and 2019 Copa América. He played 119 games and scored 50 goals for Japan until 2019.