Mexico went ahead via a North Korea own-goal in first-half stoppage time, and made it 2-0 from Taufic Guarch's 30-meter (yard) strike in the 54th minute. Diego De Buen scored the final goal from a free kick in second-half stoppage time.
Mexico has three points in two matches and North Korea has lost twice.
Mexico faces England on Thursday in Cartegena in its final Group F game, and North Korea plays Argentina in Medellin. The top two teams in each group advance automatically and are joined in the knock-out stage by the four best third-place teams.