This starfish is large and has five very spiny arms. Each arm bears three longitudinal rows of spike-like spines surrounded by large cushions of pedicellariae. Smaller spines may be scattered between these rows. The spines are white and usually purple-tipped and the animal varies in colour from dirty brown to greenish-grey with purple tips to the arms. Up to 35cm or more in diameter. Small individuals might be mistaken for Leptasterias muelleri.