Born in the northern city of Rivera, Méndez was a member of the National Party, traditionally strong in the interior of the country whence he originated.

In addition to his political life, Méndez was a close personal friend of the Spanish classical guitarist Andrés Segovia.

Méndez was one of various civilian political figures who participated in the civilian-military administration which took office following President Juan Maria Bordaberry's coup in 1973 at a time of great social tension.

Some would argue that, in agreeing to serve as president with military support, Aparicio Méndez was effectively repudiating the principles of the National Party with which he had been associated.

Others would point out that Méndez was far from alone among the various civilian party political figures who participated in the Civic-military dictatorship (1973–1985), and that he presided over a free referendum.