The coat of arms in the center of the flag shows a golden eagle perched on a nopal cactus, holding or devouring a serpent. The cactus grows from a small island in a lake, usually understood as Lake Texcoco. Around the lower part are branches of oak and laurel tied with a ribbon in the national colors.

This image comes from the founding legend of the Mexica people. According to tradition, they were told to build their city where they saw an eagle on a cactus with a serpent. That place became Tenochtitlan, the great Mexica capital, later built over and transformed into Mexico City. The coat of arms is therefore not just decoration: it ties the modern nation to pre-Hispanic history and to the origin story of its capital.