This deer can be recognized by its characteristic size, smaller than all other white-tailed deer. Adult males (known as bucks) usually weigh 25–34 kilograms (55–75 lb) and stand about 76 centimetres (30 in) tall at the shoulder. Adult females (does) usually weigh between 20 and 29 kilograms (44 and 64 lb) and have an average height of 66 centimetres (26 in) at the shoulders. The deer is a reddish-brown to grey-brown in color. Antlers are grown by males and shed between February and March and regrown by June. When the antlers are growing, they have a white velvet coating. The species otherwise generally resembles other white-tailed deer in appearance.
Key deer easily swim between islands.
Living close to humans, the Key deer has little of the natural fear of man shown by most of their larger mainland cousins. The deer are often found in residents’ yards and along roadsides where tasty plants and flowers grow. This often results in car-to-deer collisions, as the deer are more active (and harder to avoid) at night. It is not unusual to see them at dusk and dawn, especially on lightly inhabited No Name Key, and in the less-populated northern areas of Big Pine Key.