Guinea, ranked 80th in the world, had threatened a real shock when Mohamed Bayo fired them into an early lead.
But they had to play the entire second half a man light after skipper Francois Kamano stamped on Frank Magri’s heel.
Magri nodded in Georges-Kevin Nkoudou’s cross to draw Cameroon level but Guinea admirably hung on for a deserved point.
The Indomitable Stars almost snatched victory towards the end but Guinea keeper Ibrahim Kone made a fine save from Karl Toko Ekambi to ensure honours ended even.
The draw leaves both sides with work to do to qualify for the knockout stages with holders Senegal sitting top of Group C after their comfortable 3-0 victory over The Gambia earlier on Monday.
It was also another surprise outcome at the tournament in Ivory Coast after Ghana were upset by Cape Verde on Sunday while Egypt and Nigeria were held by Mozambique and Equatorial Guinea respectively.