Its plumage is entirely black with a violet iridescence, its eyes are yellow, and it has a strong dark bill.

The adult female is 23 cm (9.1 in) long, with a shorter tail and brown plumage, darker on the upperparts.

The seven island subspecies differ from the nominate one in size, plumage shade (especially in the browns of the females), and vocalisations.

It will form groups to attack potential predators, such as dogs, mongooses or humans, and at night it roosts colonially.

The Carib grackle's song is a mixture of harsh and more musical ringing notes, with a bell-like tickita-tickita-tickita-ting and a rapid chi-chi-chi-chi being typical.