Two goals each from Mohamed Zidan and Hosni Abd Rabou gave Egypt a fine start in their defence of the Nations Cup.
Cameroon were outplayed in the first half, Abd Rabou scoring from the spot and Zidan netting two superb goals.
His first came from a speedy breakaway, then he chested down and shot from outside the penalty box for his second.
Samuel Eto'o scored after the break, but Abd Rabou's long shot ended hopes of a comeback before the Cameroon striker struck home a late penalty.
Despite their status as holders, Egypt's qualifying campaign had been uninspiring, and Cameroon were expected to have the upper hand over the Pharaohs.
But Egypt began with spark and confidence, pressurising the Cameroon defence from the start of the game.
Mohamed Shawky tested Indomitable Lions' goalkeeper Carlos Kameni with a long-range shot in the third minute.
The opening goal came after 14 minutes when Andre Bikey handled in the box and Abd Rabou converted the penalty.
606: DEBATE
Zidan made it 2-0 three minutes later, breaking from inside his own half, exchanging passes with Emad Moteab and racing through the Cameroon defence before slotting home.
Four-time champions Cameroon were shocked, and there was more to come.
In first-half stoppage time, Zidan struck again, chesting the ball down outside the box and striking home powerfully.
Coach Otto Pfister decided to go for all-out attack and Eto'o gave a team talk before his side came back after the break, and Cameroon were a transformed side.
They began playing with purpose and pulled one back on 51 minutes as Eto'o headed in a Geremi cross.
He nearly added another 12 minutes later, shooting just wide.
What had been an exciting contest then slowed down, as Egypt began to dampen Cameroon's momentum.
Abd Rabou's magnificent 25-yard shot sealed the victory with eight minutes remaining.
Cameroon did score again though, with an Eto'o penalty in stoppage time.
It was Eto's 13th Nations Cup goal, leaving him just one behind the record held by Laurent Pokou of the Ivory Coast.
Egypt: El Hadari, Fathallah, Moawad (Mohamed 90), Gomaa, Hany Said, Fathi, Abd Rabou, Shawky, Zidan (El Mohamady 68), Moteab, Zaki (Aboutriaka 60).
Subs Not Used: Abdel Monssef, El Saeed, Fadl, Gamal, Hassan, Mostafa, Ibrahim Said, Shaaban, Sobhy.
Booked: Hany Said, Moawad, Fathallah.
Goals: Abd Rabou 14 pen, Zidan 16, 45, Abd Rabou 82.
Cameroon: Kameni, Song, Bikey, Atouba, Geremi, Makoun (Binya 38), N'Guemo (Emana 46), Epalle, Mbia (Song Billong 46), Idrissou, Eto'o.
Subs Not Used: Hamidou, Angbwa, Essola, Job, M'Bami, Mbarga, Nkong, Tchato, Tomou.
Booked: Binya.
Goals: Eto'o 51, 90 pen.
Ref: Modou Sowe (Gambia).
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