It was no more than the Mexicans deserved after playing the more enterprising football and having two Giovani dos Santos goals controversially disallowed for offside in the first half. Cameroon almost snatched a last-gasp equaliser but Guillermo Ochoa saved well from a firm Benjamin Moukandjo header.
With Brazil and Croatia their other opponents in Group A, Mexico will be relieved to have claimed the three points from a full-blooded encounter played in heavy rain at the Arena das Dunas. A number of hefty challenges went unpunished throughout the game by Colombian referee Wilmar Roldan but Mexico always looked the stronger side.
Peralta netted after 61 minutes and with Dos Santos also shining, the strike pair justified their selection ahead of Manchester United's Javier Hernandez.
Cameroon started poorly and rarely threatened to improve upon a record that has seen them win just once at a World Cup finals since 1990.
Mexico quickly made an impression with Miguel Layun firing over and Hector Herrera shooting at former Liverpool goalkeeper Charles Itandje from distance.
The first moment of controversy came when Dos Santos brilliantly turned in a cross from Herrera on the volley only to see a flag raised. Replays suggested the striker had been unlucky, although it was a marginal call.
Then, Eric Choupo-Moting put the ball in the net as Cameroon finally started to show some life, but there was little doubt about the offside decision that denied him.
Cameroon's purple patch proved brief and Mexico were denied by a flag again when Dos Santos stooped to head in from a Layun corner.
Dos Santos was in an offside position as the ball was swung in but the ball was diverted into his path by Choupo-Moting and not flicked on by a Mexico team-mate.
Mexico maintained their tempo after the break and Peralta was denied by a good Itanjde block, but they deservedly made their breakthrough just after the hour.
Dos Santos raced through but was denied again, this time by Itanjde, but Peralta seized on the rebound to stroke the ball home.
Cameroon searched for an equaliser, sending on striker Pierre Webo for former Arsenal midfielder Song. Rafael Marquez blocked a shot from Choupo-Moting and Francisco Rodriquez needed to stretch to intercept. Ochoa then did well to keep out Moukandjo's header but Hernandez should have made it 2-0 when he missed the target in injury time.