Frosmoth is a white, moth-like Pokémon with a round body, of which the upper half is thicker, giving it the appearance of a ruff. It has deep blue eyes and long eyelashes. It has a blue jewel between its eyes and two long antennae, which are gray at the tip with trapezoid patterns. These antennae are used to detect air currents. Frosmoth has two large wings which are gray with a white rim; the patterns on its wings are the same as that on the tip of its antennae. Frosmoth typically keeps its arms crossed, and its usually obscured palms each have a heart-shaped pad.
The ice scales from Frosmoth's wings can fall like snow while it flies over the fields and mountains. The wings have a temperature of −290 °F (−180 °C). Should anyone desecrate the fields and mountains, Frosmoth will show no mercy. Frosmoth flies around using its icy wings to create blizzards in order to chase away offenders. Frosmoth enjoys drinking clean meltwater.
Frosmoth and its pre-evolved form are the only Ice-type Pokémon in the Bug Egg Group.
Frosmoth may be based on the Gynaephora genus of alpine or Arctic moths. One particular species, the arctic woolly bear moth, can enter a dormant state that allows it to endure temperatures as low as −94 °F (−70 °C).