Monk Parakeets are highly intelligent, social birds. Those kept as pets routinely develop large vocabularies. They are able to learn scores of words and phrases. This species is considered especially adept at learning.

The nominate subspecies of this parakeet is 29 cm long on average, with a 48 cm wingspan, and weighs 100 g. Females tend to be 10-20% smaller. It has bright green upperparts. The forehead and breast are pale grey with darker scalloping and the rest of the underparts are very-light green to yellow. The remiges are dark blue, and the tail is long and tapering. The bill is orange. The call is a loud and throaty chape(-yee) or quak quaki quak-wi quarr, and screeches skveet. Domestic breeds in colors other than the natural plumage have been produced. These include birds with white, blue, and yellow in place of green. As such coloration provides less camouflage, feral birds are usually of wild-type coloration.