The Mealy Amazon has a total length of about 38-41 cm (15-16 in) and weighs 540-700 g (19.01-24.64 oz). Captives commonly are heavier. It is among the largest parrots in the Americas, mainly being surpassed by the large macaws. It has a relatively short and squarish tail, as do the other members of the Amazona genus.

The Mealy Amazon is mainly green. The back and nape often have a whitish tinge; almost as if it had been covered in a thin layer of flour ("meal" hence its name). The distal half of the tail is paler and more yellow than the basal half, thus resulting in a distinctly bi-coloured look. In flight it shows a bluish-black trailing edge to the wing and a conspicuous red speculum. Occasionally a few yellow feathers are apparent on the top of the head and two subspecies, virenticeps and guatemalae, have a bluish-tinged crown. The maroon to orange eyes (typically appear dark from a distance) are surrounded by a relatively broad white eye-ring of bare skin.

In South America, it is commonly confused with the Yellow-crowned Amazon, but can be recognized by its larger size, less yellow to the crown (not entirely reliable, as some Yellow-crowned may show almost none), the whitish tinge to its plumage, broader white eye-ring, and red of the leading edge of the wing placed near the phalanx (not near the radiale), but this is often difficult to see (especially on perched birds). Their voices are also strikingly different.

The Mealy Amazon is social and can be found in pairs or in large flocks. They are even known to interact with other parrots, such as macaws. They are usually quiet but can be loud at dusk and dawn. In captivity, they are know as one of the gentlest and calmest of all amazons.

The diet of the Mealy Amazon consists mostly of fruits, seeds, berries, nuts, blossoms, and leaf buds.

After Mealy Amazons reach sexual maturity they usually form monogamous relationships with a single partner. Each year courtship usually begins in early spring, and the female will usually lay three or four white eggs in tree-cavity nest. The female incubates the eggs for about 26 days. The male regurgitate food for the female during the incubation period, and later for the chicks in the nest as well. The chicks leave the nest about 60 days after hatching.