[4] Thromidia catalai is a large starfish with five arms and a diameter of up to 70 cm (28 in), weighing up to 6 kg (13 lb).

[2] In contrast to other members of the genus Thromidia, the tips of the arms have small, widely spaced tubercles.

[2] Thromidia catalai is found in the tropical Indo-Pacific region, its range extending from Indonesia to Hawaii, and from southern Japan to New Caledonia and northern Australia.

[2] Little is known of the feeding habits of this starfish, but related species are carnivorous with a diet mainly consisting of molluscs and echinoderms.

As with other starfishes, the sexes are separate and the eggs and sperm are liberated into the water column where fertilization takes place.