Olympiakos went in front with a superb strike by Kevin Mirallas after 23 minutes, the Belgian forward dribbling past AEK defender Kostas Manolas on the edge of the area and curling a shot into the far corner.
AEK, playing for the first time under coach Nikos Kostenoglou, rallied and levelled through an equally fine effort from Leonardo. The Brazilian beat Reds defender Avraam Papadopoulos before scoring with a powerful shot into the top corner just before half-time.
Gudjohnsen, the Iceland and former Chelsea and Barcelona forward who joined AEK in July, went off injured after 46 minutes. It was confirmed he had fractured a fibula and will be out for at least four months.
Neither AEK or Olympiakos could produce a winner in a low-key second half, and the game ended on a sour note when AEK midfielder Grigoris Makos and Olympiakos defender Francois Modesto were dismissed in the final minutes after both received second yellow cards.
Both teams have 10 points but Olympiakos, who host Borussia Dortmund in the Champions League on Wednesday, have played one game fewer.
