There are approximately six narrow creamy white bars across the tail. A Powerful Owl's Facial disc is dark brown, and surrounds bright yellow eyes with prominent eyebrows and a powerful, bluish horn beak with bristly feathers at its base. Underparts are dull white with broad brown chevrons from throat to vent, arranged in irregular bars. The tail is broadly barred brown and white. The legs are feathered to tarsus and end in huge yellow feet with brown talons.
Males are usually considerably bigger than females with broader heads and flatter crowns.
Powerful Owls always roost in the open where quite close human approach may be tolerated. Its reaction to human presence at night is often one of frozen immobility which may be maintained for hours, making it hard to, find outside breeding season. The second note is often slightly higher pitched than the first, more so in the female than in the male. The male's voice is slightly deeper than female's. There are also various other calls associated with breeding and nesting, including a strange, tremulous, sheep-like bleating uttered be either sex around the nest.