Meloetta looks like an anthropomorphic, weak Pokémon. It has musical bar-like stripes in its hair, its arms and hands resemble quarter notes, and its pupil-less eyes resemble whole notes. It has a jewel on its forehead and a black hat like a treble clef. These two treble clef-like structures are stacked together to form the shape of a wireless microphone commonly used by singers. Meloetta's long, round head is as tall as the body and nearly half as wide as the body. In both forms, Meloetta's midriff, eyes, and hair remain the same color. Meloetta is a genderless Pokémon.

Meloetta can change form when using Song of the Ancients. When in the singing mode, Meloetta can sing beautiful melodies; when in the dancing mode, Meloetta can perform elegant dances. When in the singing form, Meloetta is a normal/superpower-type Pokémon; while in the dance form, Meloetta is a normal/fighting-type Pokémon. Meloetta in dancing form will return to singing form after being substituted or the battle ends. Like many legendary Pokémon, Meloetta can become invisible.