[3] The Lesser Antillean swift is 10.5 to 11 cm (4.1 to 4.3 in) long and weighs an average of 12.7 g (0.45 oz).

It has a protruding head, a short square tail, and wings that bulge in the middle and somewhat hook at the end.

[2] The Lesser Antillean swift's breeding season appears to be in late spring and early summer.

The Lesser Antillean swift's principal call is "a high-pitched twittering trill 'prrrrrrrr' or 'prrrrrrr-titi' given at intervals.

It has a limited range and its population size is unknown but believed to be stable.