The upper breast normally remains unmarked, while the belly and undertail coverts are barred with black. The underwings are also barred with black and appear fairly dark when seen from below. The cere, eye ring, legs, and feet are bright yellow. This is the only North American falcon whose wingtips extend to, or almost to, the tail tips on perched birds. As with most birds of prey, sexes are similar in appearance, and the female is noticeably larger that the male.
Immature birds are light brown to chocolate above.
The underparts are creamy buff with heavy dark streaking. The dark brown tail has creamy, usually incomplete, bands and a wide white terminal band. The cere and eye ring are light blue, occasionally yellowish. The legs and feet vary from light blue to yellowish. The three North American subspecies are distinctive.