Crinoids and some brittle stars are passive filter-feeders, absorbing suspended particles from passing water; sea urchins are grazing herbivores and sea cucumbers deposit feeders removing food particles from sand or mud.

Crabs, sharks, eels and other fish, sea birds, octopuses and larger starfish are predators of Echinoderms. Echinoderms use their skeltons, spines, toxins, and the discharge of sticky entangling threads by sea cucumbers as defence mechanisms against predators.