Oribe Peralta scored a second-half winner in a 1-0 victory over Cameroon in rain-lashed Natal on Friday in a match which once again raised questions over the standard of refereeing at the World Cup.
Miguel Herrera's Mexico side dominated throughout but went in for the half-time break feeling aggrieved after seeing what looked like two perfectly valid goals chalked off for offside.
Those decisions did little to appease a Mexican media which cried foul after seeing Group A opponents Brazil awarded a questionable penalty in a 3-1 win over Croatia on Thursday.
But against Cameroon, whose pre-World Cup was marred by a bitter row over bonuses, Mexico were a class apart.
After a cagey start at a sodden Estadio das Dunas, Giovani Dos Santos appeared to have opened Mexico's account when he first-timed Miguel Layun's delivery past Cameroon 'keeper Charles Itandje inside the quarter hour.
But despite replays showing the Villarreal striker to be onside, the goal was chalked off by Colombian referee Wilmar Roldan.
Cameroon did not sight goal until minutes later when Eric Choupo-Moting tapped past 'keeper Guillermo Ochoa after the ball had been headed back into the box following a corner only to be ruled off side.
Cameroon eventually settled and Stephane M'Bia flashed a header wide from Alexandre Song's corner on 18 minutes.
The Africans spurned a far better chance when Tottenham defender Benoit Assou-Ekotto finished off a mazy run down the left to deliver for Samuel Eto'o, but the Chelsea striker saw his first-time shot flash wide.
Mexico remained a constant threat and when Choupo-Moting brought down Francisco Rodriguez to hand Mexico a free kick the Cameroon defence was caught unawares.
With the goal at their mercy, Rafael Marquez and Hector Moreno collided at the back post to see the ball go wide.
Mexico had the ball in the net for a second time when Dos Santos flashed a header past Itandje at the back post following a corner, although it too was waved off by Roldan.
Crowd in raptures
Cameroon coach Volker Finke replaced defender Cedric Djeugoue with Dany Nounkeu for the start of the second half, but the African side were soon under pressure.
Barely a minute after the restart Itandje was forced to block from Peralta as the Santos Laguna striker jumped on to Dos Santos's smart dink.
At the other end, Choupo-Moting saw a deflected shot come off the the foot of defender Francisco Rodriguez as Ochoa collected with ease.
Cameroon threatened on 53 minutes when a curling free kick by Assou-Ekotto, following Hector Moreno's foul on M'Bia, took a deflection off the Mexican wall to send Ochoa the wrong way but the ball flew wide.
Mexico finally had the ball in the net, this time for good, just after the hour when Dos Santos saw his low drive parried by Itandje and into the path of Peralta, who drove home from 10 metres out to send the largely Mexican crowd of 39,216 into raptures.
Coach Herrera replaced midfielder Andres Guardado with Marco Fabian and minutes later Manchester United forward Javier Hernandez came on in place of Peralta.
A chorus of 'Ole' began to ring around the stadium as the Mexicans took control, and in the final 10 minutes Hernandez chased deep in Cameroonian territory to cut back for Fabian, who was blocked by a defender.
Cameroon threatened in the final five minutes when Eto'o sent Benjamin Moukandjo through on the right but the Nancy midfielder's drive across goal was blocked by an alert Rodriguez.
Mexico had Ochoa to thank in the final two minutes when the 'keeper pulled off a spectacular dive to parry Moukandjo's header from Assou-Ekotto's delivery.
Mexico almost made it two at the death when Layun dispossessed a Cameroon defender to deliver for Hernandez, who volleyed just over.