Parasites, in particular trematodes (Platyhelminthes: Digenea), play major roles in the population dynamics and community structure of invertebrates on soft-sediment mudflats. Here, we provide a list of the 20 trematode species currently known to infect molluscs, crustaceans and polychaetes from Otago Harbour (New Zealand) soft-sediment intertidal areas, as well as information on their transmission modes, life cycles, andknown ecological impacts. Several of the host-parasite species combinations recorded here are reported for the first time. We also provide DNA barcodes, based on sequences of the cytochrome oxidase subunit l (CO1) gene, for 19 of the 20 trematode species, to facilitate future identification of these parasites in marine ecological studies.