Calafeteanu had his first game for Romania, on 20 November 2004, with Japan, in a 25-10 win, aged only 19, in a friendly.
He holds 72 caps for Romania, with 11 tries, 27 conversions, 33 penalties and 1 drop goal scored, on an aggregate of 211 points. He won the European Six National Championship Cup, Group B, in 2006. He played all the four games, three of them as a substitute, at the 2007 Rugby World Cup finals, where he scored a conversion in the 14-10 win over Portugal. He was called for the 2011 Rugby World Cup, playing in three games but without scoring. He was called once again for the 2015 Rugby World Cup, playing in all the four games.