Diplectanum parvus sp. nov. is described from the coral reef fish Cephalopholis urodeta collected off New Caledonia, South Pacific, and is the first diplectanid described from this fish. The new species has a very small male copulatory organ (24 μm in length) and a minute body (246 μm in length) and is close to D. nanus Justine, 2007 from which it can be distinguished by the shape of dorsal bars and various measurements. These species belong to a group of diplectanids found in groupers (Serranidae, Epinephelinae), characterised by small funnel-shaped male copulatory organs and no sclerotized female organs. The attribution of these parasites to Diplectanum Diesing is provisional. Other parasites are briefly listed.