FIBA Europe
With Greece's junior national teams, Giannakidis played at the following tournaments: the 2004 FIBA Europe Under-16 Championship, the 2005 FIBA Europe Under-18 Championship, the 2006 FIBA Europe Under-18 Championship, the 2007 FIBA Europe Under-20 Championship, and the 2008 FIBA Europe Under-20 Championship.