Egypt defender Abdel-Moneam. AFP
Sofiane Boufal converted a sixth-minute penalty to give Morocco an early lead but Mohamed Salah brought Egypt level eight minutes into the second half.
The Liverpool talisman then set up Mahmoud Trezeguet for a 100th-minute winner as Egypt set up a semi-final clash with hosts Cameroon on Thursday.
"We were very nervous in the first half and we made many mistakes," Abdel-Moneim told beIN sports after the game.
"We were determined to regain our composure, and that was our secret for the win."
Abdel-Moneim proved one of Egypt's standout performers at the Nations Cup despite his little international experience. He was given a chance to prove his worth after Zamalek's Mahmoud El-Wensh picked up an injury in the 1-0 group-stage win over Guinea-Bissau.
Short link: