In the summer of 2015, Charalampopoulos suffered a right ankle injury in a friendly game against the USA, and doctors initially said that it would be difficult for him to play at the 2015 FIBA Under-19 World cup. Despite the injury, Charalampopoulos was able to play at the tournament, and he scored 21 points against the US in the tournament's semifinal. Greece lost the semifinal game against the US, and Charalampopoulos was then injured once again in the third-place game, against Turkey, which Greece also lost, as they finished in fourth place.