Butterfree resembles a vaguely anthropomorphic butterfly with a purple body. Unlike true insects, it only has two body segments and four light blue legs. The upper pair of legs resemble small, three-fingered hands, while the lower pair resemble long, digit-less feet. Butterfree has two black antennae, a light blue snout with two fangs underneath, and large, red compound eyes. Its two pairs of veined wings are white with black accents. The oval scales of a female Butterfree's lower wings are black, but white in males.
Butterfree's wings are covered with poisonous powders that fall off continuously as it flies. This powder repels water, enabling it to gather honey even in the rain. Butterfree will roam up to six miles from its nest in search of honey, which it carries with the hairs of its legs. It also consumes sap from trees pierced by Heracross. Butterfree is found in forests, but has also been observed flying near the ocean as part of its migratory breeding pattern.
Butterfree is a combination of butterfly and free, possibly referring to its ability to fly after being grounded for two evolutionary stages. In Japanese, the name may also derive from the word 振る furu (to flap, as in wings).