The mosaic sea star is a five-armed sea star distinguished by its geometric patterns, which form a mosaic with very bright yellow or even whitish seams. Its main color is generally bright red, but the mosaic sea star can sometimes display a darker red coloration as well as areas of different colors.

The mosaic sea star is a sea star endemic to the southern coast of Australia. It is found from Perth on Australia's west coast to Brisbane on the east coast, passing through Adelaide, Melbourne and Sydney.

The mosaic sea star inhabits rocky reefs at depths ranging from 33 feet to more than 492 feet.

The mosaic sea star feeds mainly on sponges.

The mosaic sea star is one of the few venomous sea star species. It can cause numbness in humans when handled for an extended period of time.