Oribe Peralta grabbed the only goal after 61 minutes but Mexico will consider themselves unlucky not to have been more comfortable winners after Giovani Dos Santos had two goals ruled out for dubious offside decisions in the first half.
On both occasions, it was former Tottenham striker Giovani Dos Santos who was the victim.
In the 11th minute, the Villarreal player found the target with a sweet, stabbed volley from a cross by Porto’s Hector Herrara but his effort was ruled out by Colombian referee Wilmar Roldan
On the 30-minute mark, a Dos Santos header from a corner by Miguel Layun was also not allowed to stand.
In between, Cameroon skipper Samuel Eto’o had a goal chalked off for offside although this time the referee made the right decision.
The blunders came just a day after Japanese referee Yuichi Nishimura controversially awarded a penalty which set Brazil on their way to a 3-1 win over Croatia.
Eto’o had Cameroon’s best chance of the first half after 21 minutes but narrowly went wide of the post.
Early in the second period, Mexico had a golden opportunity when Peralta was clean through on goal, but he fired the ball straight at Charles Itandje in the Cameroon goal.
Peralta deservedly put Mexico in front just after the hour mark. Dos Santos’s shot was parried into his path and the Club Santos Laguna striker slotted in from close range.
Cameroon’s Benjamin Moukandjo had a chance to rescue a point in injury time but his header was well-saved by Guillermo Ochoa.
Mexico next face Brazil in Fortaleza on Tuesday with Cameroon taking on Croatia the following day.