Adults have a dark slate- blue back and wings and a dark blue tail that is lightly barred.
The top of the head is dark with a dark line running down the side of its face. The legs and feet are bright yellow. The bottomside of the adult is light with vertical streaks across the breast, belly, and legs. Immatures are uniformly brown on the back, top of the head, and wings with a light underside streaked with brown. Recently many cities with tall buildings have become home to couples of peregrines.