The Club America striker sealed victory for his side after Giovani dos Santos had two goals disallowed in controversial offside decisions
The Club America striker now has nine goals from his last seven competitive matches for Mexico as he put his side second in Group A after a hard-fought victory.
Amid heavy rain in Natal, the opening 45 minutes saw plenty of goalmouth action - although much of it came courtesy of three disallowed efforts.
Giovani dos Santos had two ruled out by referee's assistant Humberto Clavijo, both of which seemed close calls, while Eric Maxim Choupo-Moting also had one chalked off in a goalless opening half.
Just after the hour, Mexico eventually got their breakthrough when Peralta snaffled up a loose ball inside the area.
Peralta, scorer of 10 goals in Mexico's qualification campaign, secured his first at a World Cup and it proved enough for Miguel Herrera's side to keep pace with Brazil at the top of the group.
Mexico made much of the early running, although Miguel Layun's tame effort on target was easily saved by Charles Itandje.
Dos Santos then looked to have opened the scoring when he side-footed home after 11 minutes, only to be adjudged offside from Rafael Marquez's delivery.
The likes of Dos Santos and Peralta proved a threat for Mexico as Cameroon struggled to get out of their own half in the opening 20 minutes.
It was then Cameroon's turn to have a goal ruled out - with Choupo-Moting judged to have strayed offside.
Benoit Assou-Ekotto produced a golden opportunity for Cameroon as he surged down the left wing before pulling a cross back that Samuel Eto'o could only fire wide.
It marked a first spell of dominance for Volker Finke's men, but Mexico could have taken the lead had captain Marquez left a delivery for the onrushing Hector Moreno after a teasing delivery from the right.
Dos Santos had the ball in the net for a second time before the break, but again he was denied after Clavijo deemed the flick-on to come from Hector Herrera rather than Choupo-Moting.
Having been among the talking points at half-time, the officials were soon back in the limelight when referee Wilmar Roldan was required to produce a yellow card for a poor challenge from Alexandre Song on Dos Santos.
Assou-Ekotto went close with a deflected free-kick just before the hour, but, when Dos Santos' shot at the other end was only parried by Itandje, Peralta was on hand to tuck away the decisive goal.
Eto'o cleverly played in Benjamin Moukandjo behind the Mexican defence late on, but his cross was cleared by Francisco Rodriguez. Moukandjo also had a header well saved by Guillermo Ochoa.
Javier Hernandez then blazed a shot off target from close range in stoppage time, but it mattered little as Mexico stood firm to bolster their hopes of reaching the last 16 for a sixth World Cup running and leave Cameroon with a mountain to climb.