A match that struggled to spark into life was ultimately decided by a costly goalkeeping error early in the second half, allowing Luis Romo to score the only goal and continue Mexico's impressive start to the tournament.
After opening their campaign with victory over South Africa, Javier Aguirre's side faced a much sterner challenge against the Koreans. The first half was closely contested, with clear chances at a premium.
Mexico came closest to breaking the deadlock before the interval when Roberto Alvarado delivered a dangerous cross that Julian Quinones directed towards goal, only for goalkeeper Kim Seung-Gyu to react well and make the save. South Korea also threatened through Son Heung-min, but his effort was ruled out after an offside flag had been raised.
With both teams having won their opening matches, neither side appeared willing to take major risks during a cautious first half.
The decisive moment arrived less than five minutes after the restart. Kim Seung-Gyu unexpectedly dropped a routine aerial ball inside the penalty area, gifting Romo a simple finish into an unguarded net for his first goal in a major international tournament.
South Korea struggled to respond for much of the second half, lacking the attacking urgency needed to trouble the hosts. Their best opportunity came late on when Cho Gue-sung was denied from close range by Mexico goalkeeper Raul Rangel.
Mexico held firm to secure a second successive win and maintain their perfect World Cup record against Asian opposition.
The victory delighted coach Javier Aguirre, who revealed that finishing top of the group was a major motivation for his players.
"I don't like to depend on others," Aguirre said. "The players knew that if we won, we would finish top and play at the Azteca, which is amazing for us."
The veteran coach believes the famous Mexico City stadium could play a huge role in his team's knockout-stage ambitions.
"The Azteca factor is quite significant," Aguirre added. "Forty years ago, the stadium was like a volcano. Playing there involves the whole Mexican republic."
Aguirre, now managing Mexico at his third World Cup, also credited experience for his calmer approach on the touchline.
"The team's head coach is much cooler and more relaxed now," he said. "In previous World Cups I worried about many things. Now I focus on what really matters."
Mexico will play the Czech Republic next in their final 2026 FIFA World Cup group stage match.