Two new species of the family Diplectanidae Monticelli, 1903 from the gills ofProtonibea diacanthus(Lacepède, 1802) (Teleostei: Sciaenidae) off the northern Australian coast are described. Previous studies have either morphological or genetic results, whereas this study combines morphological and advanced molecular methods to provide the first detailed descriptions for species ofDiplectanumDiesing, 1858 from Australia utilising both methodologies. Two new species,Diplectanum timorcanthusn. sp. andDiplectanum diacanthin. sp., are morphologically described and genetically characterised using the partial nuclear 28S ribosomal RNA gene (28S rRNA) and the internal transcribed spacer 1 (ITS1) partial sequence.