The colour of the upperparts varies from grey-brown to dark brown and may appear bluish in dull light. The forehead is creamy white and the crown and nape finely spotted creamy white. The back and wings are irregularly barred, also in creamy white. 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.