This chapter explains that addressing national security is a matter of just a few decades in Mexico, whose discussion was delayed by both the discredit of the concept in South America during the Cold War and the need to prevent the United States from identifying its security interests with those of its neighbor to the south, under a dominant nationalist ideology. The country has a predominantly inward-looking “national security” perspective explained by both its geopolitical situation and the demilitarization of its political system. The opening of its economy since the mid-1980s and a closer economic relationship with the United States, nevertheless, have increasingly exposed the country to developments beyond its borders and, therefore, it needs to adapt its national security perspective accordingly.