The changeable hawk-eagle is a slender, medium-sized eagle. Adults are dark brown above with bold streaks below, a strong bill, and long feathered legs. They often have a floppy crest, and the Sri Lankan subspecies typically has a longer crest. Juveniles have a lighter brown tail with dark bars and a whitish tip. These raptors are ambush predators, using foliage for concealment as they pounce on prey from branches. Breeding season runs from November to June, peaking between January and March. They build large, sturdy nests and lay one egg, with the female incubating for around 40 days.