Nigeria top Group B with 10 points from four games, six ahead of second-placed Zambia, who visit Algeria on Wednesday.
With only the top team going to Russia, Cameroon have three points from four games and cannot overhaul Nigeria, who had Belgian-based forward Moses Simon to thank for their goal.
Algeria have only the slimmest chance of overhauling Nigeria, having picked up one point from three games.
Ghent midfielder Simon gave Nigeria the lead when he blasted home at the back post on the half-hour. Their Chelsea winger Victor Moses also struck the bar in the second half.
Cameroon equalised with a penalty 15 minutes from time when Vincent Aboubakar converted after Nigeria goalkeeper Ikechukwu Ezenwa upended midfielder Arnaud Djoum.
Cameroon had qualified for six of the last seven World Cup tournaments since reaching the quarter-finals in 1990, last missing out in 2006.
They were surprisingly crowned African champions in Gabon this year under Belgian coach Hugo Broos, but have only managed three draws and a defeat in their four World Cup qualifiers.
(Reporting by Nick Said; editing by Ken Ferris)
