The Indomitable Lions had Frank Magri to thank for ensuring they took a point from their Group C opener in Yamoussoukro on Monday evening, with the Toulouse forward heading in Georges-Kevin Nkoudou's delightful deep left-wing cross from close range early in the second half.
Guinea had earlier gone ahead inside just 10 minutes through Mohamed Bayo, who slotted low beyond Fabrice Ondoa at the second attempt after fierce pressing to force a costly error from Olivier Kemen on the edge of his own box.
Cameroon appealed for a foul that never came after an initial strong save from Ondoa - cousin of Andre Onana, who was not in the squad after his late arrival from Manchester United was further delayed by travel chaos - to deny Bayo and a huge challenge from Harold Moukoudi on Ilaix Moriba.
Guinea's hard work looked to have been undone on the stroke of half-time, when forward Francois Kamano - wearing the captain's armband with usual skipper Naby Keita only on the bench - saw his yellow card for treading on the back of Magri's ankle upgraded to red after the referee consulted the pitchside monitor.
But while Cameroon dominated the second half and got their equaliser just six minutes after the break, they could not make their numerical advantage count thereafter.
They didn't even manage to create much by way of clear-cut chances without injured captain Vincent Aboubakar, with former Tottenham winger Nkoudou glancing a header wide and Karl Toko Ekambi forcing a solid late save from Ibrahim Kone.
The result would certainly seem to suit defending champions Senegal, who made a strong start to the so-called 'Group of Death' earlier on Monday when they brushed aside The Gambia 3-0 thanks to a brace from Lamine Camara.
The Lions of Teranga meet Cameroon in their next match on Friday, before Guinea - who were without star striker Serhou Guirassy on Monday due to injury - take on The Gambia later in the evening.