The spectacled owl is a medium sized owl, standing 16-to-19 inches tall. The plumage is mostly dark brown, with a yellowish belly, a white patch on the neck front and a dark brown belt across the chest. White "spectacles" around the yellow eyes give the bird its name. The juvenile has adult markings in reverse, a white head with black mask, and may take several years from hatching to attain full adult plumage. Usually nocturnal, the bird can be active on dull days. Using a branch to perch on and scan the area, the bird drops with a swift pounce onto located prey. Insects are snatched from foliage

Vocalizations consist of a series of knocking or tapping sounds with a popping effect, each successive note lower and weaker, with a quickened rhythm as the series progresses. The female also has a hawk-like scream, which sounds something like a steam whistle.

The nest is built in a hollow tree hole. The female lays two white eggs, which are incubated mostly by her for about 32 days. The chicks leave the nest for surrounding branches well before they can fly, but depend on the parents for food and protection for up to a year after fledging. Usually, only one chick survives.

In Brazil, the spectacled owl is known as a “knocking owl” because its call sounds like woodpecker tappings. The juvenile, with its white plumage and black face is referred to as a “ghost owl.”