In June 2014, Papastathopoulos was named to Greece's squad for the 2014 FIFA World Cup. He started in each of the team's group matches, helping them to a clean sheet against Japan. In the round of 16, Papastathopoulos scored his first international goal, equalising in second half stoppage time against Costa Rica. However, the Greeks were eventually defeated 5–3 in a penalty shoot-out by the Central American champions.