[6][7][8] Actinopyga agassizii is found in the tropical Western Atlantic region, its range extending from the Gulf of Mexico to the Caribbean Sea.

It is nocturnal and inhabits rocky areas, coral reefs, and sea grass beds at depths between 0 and 54 m (177 ft).

[1][6] Actinopyga agassizii feeds on detritus on algal turfs and sea grass beds and in sandy or rocky areas.

Its life cycle consists of the embryo growing into a free-swimming larva before developing a barrel-shaped body and later undergoing metamorphosis to turn into a juvenile sea cucumber.

As a mode of self-defence, it can expel clusters of sticky threads called Cuvierian tubules which contain a toxic saponin named holothurin that can paralyze other animals.