A new species of the demersal calanoid copepod genus Pseudodiaptomus was collected from The Great Barrier Reef, Australia during 1978 and 1989 by several australian researchers at different times. This species is one of the larger pseudodiaptomid species within the genus and was initially thought to be P. ornatus, which is mainly known from northwestern Pacific waters. This new species belongs to the ‘Improcerus’ species group (Walter 1986) and is the 16th species of this genus reported from Australia and surrounding neighboring waters.