Three species of Anisakis from Australian marine mammals, including Anisakis brevispiculata, A. simplex C and A. pegreffii, are described and characterised genetically on the basis of sequence data for the first and second internal transcribed spacers (ITS-1 and ITS-2) of nuclear rDNA. Parasite specimens were collected from Delphinus delphis, Tursiops truntatus and Kogia sima in Australia. A. brevispiculata is reported for the first time in Australia. However, analyses of sequence data suggests that A. brevispiculata in Australia is genetically distinct from specimens considered to represent the same species from other parts of the world. Fourth larval and adult stages of A. pegreffii were found in dolphins. Assigning larvae to A. pegreffii was based on the ITS-1 and ITS-2 sequences. A description of these larvae also is provided. Furthermore, fourth-stage larvae of A. simplex C were found in Kogia sima. Alignments of ITS-1 and ITS-2 sequences for members of A. simplex sensu lato revealed that nucleotide differences in ITS-1 can be used to differentiate among members of A. simplex sensu lato. This study reinforces the use of a combined molecular and morphological approach for the specific identification of anisakid nematodes.