[1] Kostner has represented the Italian national team in several tournaments.

His first International Ice Hockey Federation (IIHF)-sanctioned event was the 2007 World U18 Championships Division I. Italy placed fourth in the Group A tournament while Kostner recorded one assist in five games.

He returned the following year to the 2008 Division I tournament; playing in Group A Italy finished fourth again and Kostner, serving as captain, had 7 points in 5 games.

Kostner was born in Bolzano, and grew up in Northern Italy.

This Italian biographical article relating to ice hockey is a stub.