As a member of the senior men's Greek national basketball team, Zisis won the gold medal at the 2005 EuroBasket, which was held in Serbia and Montenegro. He was Greece's leading scorer during the tournament, averaging 10.6 points per game. At the end of the semifinal game against the French national basketball team, Zisis drove the length of the court, drove into the middle of the floor, drew a double team, and then dished the ball out to Dimitris Diamantidis, who hit a game-winning 3 pointer. After his great performance at the EuroBasket in 2005, Zisis was named the FIBA Europe Young Player of the Year.