Species of Harmothoe are found world-wide to depths of at least 5,000 m but are more common in shallower water.

[1] Body dorsoventrally flattened, short, with 15 pairs of elytra and up to 50 segments; the body is more or less covered by elytra, although long specimens may have a short posterior region uncovered.

The prostomium is rounded anteriorly and has distinct cephalic peaks on the dorsal surface.

The notoochaetae are stout with transverse rows of spines and blunt tips.

[3] In many parts of the world, identification of species in this diverse genus is problematic, however recently published revisions provide a guides to species of Harmothoe from the Mediterranean,[2] Northeast Atlantic[4] and from the Subantarctic and Antarctic.