Owlet-nightjars are insectivores which hunt mostly in the air but sometimes on the ground; their soft plumage is a cryptic mixture of browns and paler shades, they have fairly small, weak feet (but larger and stronger than those of a frogmouth or a nightjar), a tiny bill that opens extraordinarily wide, surrounded by prominent whiskers.

A comprehensive 2003 study analyzing mtDNA sequences of Cytochrome b and ATPase subunit 8 suggests that 12 living species of owlet-nightjar should be recognized, as well as another that became extinct early in the second millennium AD.

It appears though that they are not as closely related to either as previously thought, and that the owlet-nightjars share a more recent common ancestor with the Apodiformes.

Owlet-nightjars are an exclusively Australasian group, but close relatives apparently thrived all over Eurasia in the late Paleogene.

Dating from the Early to Middle Miocene (Altonian, 19–16 million years ago), it seems to represent an owlet-nightjar ancestral to A.