 Vlaar represented the Netherlands at various youth levels.However, he had most success with the Netherlands U20 on the 2005 FIFA World Youth Championship and with Netherlands U21 on the UEFA European Under-21 Football Championship in 2006 and 2007

The 2005 FIFA World Youth Championship took place in the Netherlands between 10 June and 2 July 2005.Vlaar, reserve captain behind Hedwiges Maduro, was an important player in the Dutch team and was active in every match the team played on the tournament.