A shaky warm-up campaign had called into question the dominant form the Germans showed in qualifying, but experience and records were on their side, having won every opening game at major tournaments since Joachim Loew took over as coach in 2006.
Juan Carlos Osorio's side had other ideas, however, holding their own against the favourites' fearsome but slowing midfield and finding space at the back and seeking to end 33 years without a win against Germany. After wasting a handful of first-half chances while living dangerously in their own half, Hirving Lozano's 35th-minute strike on the break proved just reward.
When centre back Mats Hummels lost possession deep in the Mexican half, Javier Hernandez was released through the middle. He outpaced Jerome Boateng and with a less than perfect pass found Lozano, who controlled the ball, cut inside Mesut Ozil, held off a charging Toni Kroos and slotted past Manuel Neuer.
At the other end, Guillermo Ochoa tipped a blistering Kroos free kick on to the bar minutes later, in what was to prove the Germans' closest effort of a match in Moscow in which they had more than 60 percent possession but could not make it count.
"Our motto was play with the love of winning and not the fear of losing," said a delighted Osorio.
For Loew, "we played badly", gave the Mexicans too much space, lost too many balls and rushed chances under pressure.
"It's an unfamiliar situation," he said, while insisting the team "has enough experience to not go under with one defeat".
"But the next game is now more important," he added of Saturday's clash with Sweden. "We have to win."
Finishing second in the group could well mean facing Brazil rather than Switzerland or Serbia in the next round.
"Mexico deserved the win," Hummels conceded.
PRESSURE
Germany pressed in the second half but struggled to find the target and Osorio bolstered his lines, pulling off Lozano and, with a quarter-hour left, sending on 39-year-old defender Rafael Marquez to become the third man ever to play in five World Cups.
Loew threw on Marco Reus in place of Sami Khedira and, with 10 minutes to go, yet another striker in Mario Gomez, to reinforce Timo Werner, who had failed to make much of a mark.
Mexico had much of the 80,000 crowd in Luzhniki Stadium on their feet as the Germans left ever greater gaps at the back, and the wastefulness notably of Hernandez on the final pass may reassure future opponents that Mexico, while determined to end a Cinderella reputation, have not replaced Germany as favourites.
Youngster Julian Brandt nearly saved Loew's night in the final minutes when he blasted a shot past Ochoa's right post.
But it was not to be.
With talk back home of a "historic victory" and sombrero-wearing supporters brightening and deafening the summer streets of Moscow, Mexico can dream of going better than a consistent record of reaching the last 16 of the last six World Cups and a couple of quarter-finals.
The Germans, branded an "embarrassment" in their home press, should still qualify, with a final group game against South Korea. And there is plenty of historical precedent for teams going on to do well after losing an opening game.
But their reputation is not what it was. And coming second could well see the four-times champions face the five-times World Cup winners Brazil if the latter win Group E.
"We are now under pressure," Kroos said. "We have to get six points from the next games."
(Reporting by Alastair Macdonald ; @macdonaldrtr; Editing by Hugh Lawson)
