 In 2008 Giannou represented the Greece under-19 team at the 2008 UEFA European Under-19 Football Championship elite qualification where Greece qualified for the Championship finals, he played alongside Australian Dean Bouzanis.Under coach Alexis Alexiou, Giannou appeared twice at the European Under-19 Championships when he was substituted on in a 1–1 draw against Italy and started in a 3–0 loss against England as Greece finished at the bottom of their group.On 5 September 2010 Giannou returned to the international stage after two years' absence, he was selected for the Greece under-21 team for a 2011 European Under-21 Championship qualifier against the Macedonia which Greece won 2–1.