Greece midfielder Mantalos headed home a Ronald Vargas cross seven minutes before the break inside an eerily silent Olympic Stadium without any fans due to crowd violence that has blighted this season's competition.
Djebbour added a second against his former club five minutes after halftime from a Vargas through ball in a match that took place at the third time of asking following two postponements.
Alejandro Domiquez gave Olympiakos hope with a superb goal five minutes from time but AEK held on to claim a 15th Greek Cup win, denying Olympiakos an 18th double in the process.
It was AEK's first trophy since a 2011 Cup triumph and marked an impressive return to success for Stelios Manolas' men after bankruptcy and relegation to Greece’s third tier in 2013.
“For me this trophy is the prize for the difficult times the club has gone through this past few years -- this club is back and has deservedly won the cup,” said Mantalos.
SHAMEFUL SITUATION
Marco Silva’s Olympiakos, who had not been in competitive action since beating AEL Kalloni 5-0 in their final league match on April 17, dominated possession in a rather pedestrian affair.
However, the Piraeus club looked understandably out of sorts and short of match practice due to the delays as opposed to AEK, who are still in competitive action in the playoffs.
“The fact that we waited for a month to play this game is proof that Greek football needs much improvement. What happened is shameful, it’s not right and is very bad for the game here,” said a fuming Silva.
"The season hasn’t ended in the best way for us. We were not at all on the ball today and couldn’t find any rhythm, but what has happened in the last few months in this competition has not happened anywhere else."
The game was originally scheduled for April 24 but was moved to May 7 after a high-profile postponement by the government. The match was then once again controversially postponed at the request of the police due to a nationwide 48-hour strike.
Greece’s Deputy Minister for Sport, Stavros Kontonis, had cancelled the competition outright after the first leg of the semi-final between PAOK Salonika and Olympiakos on March 2 was abandoned due to a pitch invasion.
However, Kontonis reversed his decision last month after soccer's world ruling body FIFA and its European counterpart UEFA warned that the country would be suspended from international football if the Greek Cup did not resume.
The competition restarted with the remaining games played behind closed doors for security reasons.
(Reporting by Graham Wood, editing by Ed Osmond and Ken Ferris)
