1 February 1966|
Vassaras became a FIFA referee in 1998, and refereed his first senior international in 1999, in a match between Austria and San Marino. That same year, he was selected as one of the referees for the FIFA World U-17 Championships in New Zealand. He was named as a UEFA Elite Referee in 2004 and, since then, has officiated matches in the UEFA Champions League, the European Championships and the Olympic Games.
In 2009, after being left out of the list of European referees to officiate at the 2010 FIFA World Cup due to his age, he decided to completely retire from officiating.