The adult threespot damselfish is a brownish-grey, bony fish with a dusky yellow sheen and a large black spot at the base of the pectoral fins.

It is a demersal fish, and its favoured habitats are inshore and offshore coral reefs.

[3] Threespot damselfish feed mainly on seaweed, but also eat copepods, gastropod molluscs and their eggs, hydroids, marine worms, and sponges.

[3] Adults vigorously maintain large territories, chasing away and nipping intruders, including humans.

The female lays eggs which stick to objects on the seabed, and the male guards these and oxygenates them by fanning them with its fins.