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.
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.