 Mavrokefalidis started his professional career with PAOK, after moving to Thessaloniki from Kilkis, where his parents come from.From the first days of his professional career, PAOK head coach Bane Prelević took advantage of his height and decided to play him at the center position, which, as it was proved later in his career, fit him very well.Mavrokefalidis played for PAOK in the Greek Basket League during the Greek League 2005–06 season, averaging 16.7 points and 8.4 rebounds per game.