Male northern hawk-owls are generally 36–42.5 cm (14.2–16.7 in) long and weigh about 300 g (11 oz).
Females are slightly bigger with a length of 37.2–44.7 cm (14.6–17.6 in) and a mass of about 340 g (12 oz).
Both male and female have similar wingspans of about 45 cm (18 in).
The northern hawk-owl plumage is relatively dark brown with an off-white spotting pattern on all dorsal parts of the body with the exception of the back of the neck which boasts a black v-shaped pattern.
The underbelly is generally white or off-white which continues to the toes with brown bands on the breast and stomach.
It also boasts a long tail with brown banding.
The northern hawk-owl has a smokey white face with a black border, a flat head, yellow eyes and a yellow curved beak.

The northern hawk-owl has been said to resemble a hawk in appearance and in behavior.
In North America, its appearance in flight is often considered similar to a Cooper's hawk (Accipiter cooperii).
It has been suggested that this may be because the hawk-owl may partially fill an important diurnal niche similar to that of day hunters such as hawks.
Male northern hawk-owls are generally 36–42.5 cm (14.2–16.7 in) long and weigh about 300 g (11 oz). Females are slightly bigger with a length of 37.2–44.7 cm (14.6–17.6 in) and a mass of about 340 g (12 oz). Both male and female have similar wingspans of about 45 cm (18 in). The northern hawk-owl plumage is relatively dark brown with an off-white spotting pattern on all dorsal parts of the body with the exception of the back of the neck which boasts a black v-shaped pattern. The underbelly is generally white or off-white which continues to the toes with brown bands on the breast and stomach. It also boasts a long tail with brown banding. The northern hawk-owl has a smokey white face with a black border, a flat head, yellow eyes and a yellow curved beak.
The northern hawk-owl has been said to resemble a hawk in appearance and in behavior. In North America, its appearance in flight is often considered similar to a Cooper's hawk (Accipiter cooperii). It has been suggested that this may be because the hawk-owl may partially fill an important diurnal niche similar to that of day hunters such as hawks.
Northern hawk-owl