The Hull City striker Daniel Cousin took advantage of a defensive mix-up to grab the only goal after 17 minutes, and no amount of Cameroon pressure thereafter could produce an equaliser. The victory was only Gabon's second ever in a Nations Cup match. In another Group D encounter, Zambia and Tunisia played out a 1-1 draw. J Mulenga gave Zambia the lead in the 19th minute before Z Dhaouadhi equalised five minutes from halftime.
Cameroon did all the early pressing, with Landry N'Guemo going close from a tight angle before Didier Ovono had to turn Achille Emana's snap shot on to the post and out for a corner. It was against the run of play when Gabon snatched the lead with less than 20 minutes gone. Cameroon's defence got themselves in a mess, allowing a miskicked pass from Cedric Moubamba to find its way into the path of Cousin, who slipped a low shot past Carlos Kameni.
Cameroon almost responded moments later as Alex Song surged forward. The midfielder was brought down on the edge of the area but the South African referee waved play on as the ball fell for Pierre Webo, who saw his low shot saved.
Geremi's long-range freekick then seemed to have Ovono in trouble, but he awkwardly punched it away. The second half took time to come to life but Emana almost scored an explosive equaliser with a long-range half-volley out of nothing that flashed wide of the goal.
A quick freekick just before the hour mark released Emana inside the area but as he closed on the goalkeeper he sliced his shot horribly wide. Cameroon were struggling to get their star striker, Samuel Eto'o, involved and his first decent shot from inside the area was deflected wide.
Emana then forced a good save from Ovono before the substitute Somen Tchoyi flashed a powerful shot wide, but it was beginning to look like it might not be Cameroon's day after all.
Ovono made an excellent save to keep out Geremi's deflected free-kick in the 90th minute and Song then sent Cameroon's last chance over the bar. Gabon almost sealed it when Pierre-Emerick Aubameyang smashed the ball against the crossbar in injury time, but Cousin's strike proved enough on the day.