Gurney’s eagles are entirely dark brown to black. The wings and tail are long; they have a large head and beak. The eyes and legs are yellow, and the cere is grey.

Juveniles have brown scapular feathers, wing coverts and back, mottled with grey and buff. The black tail is faintly barred, and the head and underparts are light brown fading into a cream-coloured belly and legs.