Four new carotenoids, named 4-ketodeepoxyneoxanthin (1), 4-keto-4'-hydroxydiatoxanthin (2), 3'-epigobiusxanthin (3), and 7,8-dihydrodiadinoxanthin (4), were isolated from the crown-of-thorns starfish, Acanthaster planci. Their structures were determined on the basis of chemical and spectroscopic data.