Tsalmpouris was a member of the junior national teams of Greece. With Greece's junior national teams, he played at the following tournaments: the 2012 FIBA Europe Under-16 Championship, the 2014 FIBA Europe Under-18 Championship, the 2015 FIBA under-19 World Cup, the 2015 FIBA Europe Under-20 Championship, and the 2016 FIBA Europe Under-20 Championship Division B, where he won a bronze medal.