In the present investigation, co-invasion of Lernaea parasite is reported in some fish species, collected from the Kor River Basin (Dorudzan Reservoir and Kor River), Southwest of Iran in 2010 and 2011.  Lernaea cyprinacea parasites were isolated from the external surface of eye, lips, gills, nostrils, fins, operculum and body of Alburnus mossulensis, Capoeta aculeata, Capoeta saadii (all native cyprinids), Cyprinus carpio and Carassius auratus (exotic cyprinids). The highest infestation was found in endemic fish, C. aculeata with 61ectoparasites in a single specimen of 348 mm TL. The greatest prevalence was found in C. auratus (100%) followed by C. saadii (80%), C. aculeata (69.4%), C. carpio (30.1%) and A. mossulensis (27.3%). Lernaea parasites may have been translocated into Dorudzan Dam by exotic species (e.g., C. carpio and C. auratus) through the four processes of introduction (transport in alien host and acting as co-introduced species), establishment (survival and reproduction in alien host, acting as co-introduced species), spreading with its original host (dispersal) and switching to a native host species to become a co-invader.