Alien parasites introduced via invasive fish species (co-invaders) pose one of the most important threats to freshwater fishes throughout the world. Two of the most invasive fish species in Australia are Cyprinus carpio (common carp) and Carassius auratus (goldfish). In February, 2018, as part of a feral fish control program, 65 goldfish and koi carp were removed from a lake in Perth, Western Australia. Fish intestines/stomachs were screened for parasites by microscopy and molecular tools, as part of ongoing PhD research on Giardia and Cryptosporidium. Analysis revealed that 12.31% of the fish (6 carp and 2 goldfish) were parasitized with large numbers of intestinal worms. Microscopic and molecular evidence confirmed the species to be the Asian fish tapeworm (Schyzocotyle (= Bothriocephalus) acheilognathi). This is the first report of this parasite in Western Australia. The parasite has a wide host range, is highly pathogenic and frequently causes mortalities, which raises major concerns for the unique and threatened native freshwater fishes of the region.