It is mainly present in the lower algal zone, dominated by the kelps Lessonia nigrescens and Durvillaea antarctica and various encrusting coralline algae.

These starfish are the dominant carnivores in this zone and seem to play an important role in maintaining the community structure.

[3] Besides being a predator of sessile organisms, P. chilensis is an opportunistic feeder, scavenging for dead animal matter and detritus.

It is a small species, and avoids being preyed on by the larger starfish by tending to remain in concealed locations.

The opening of a new sea outlet from a copper mine at Caleta Palito in Chile in 1975 caused mass mortality of the starfish Stichaster striatus, Meyenaster gelatinosus and Patiria chilensis and the sea urchin Tetrapygus niger, which disappeared completely from the area.