An investigation was conducted from November, 2010 and August, 2011 in Lake Lugo (Hayke), northeast Ethiopia, with the aim of determining the prevalence and identifying the species of internal parasites from freshwater fish. A total of 412 randomly selected fishes comprising of 225 Oreochromis niloticus, 72 Clarias gariepinus and 115 Cyprinus carpio were examined for internal helminthes parasites. An overall prevalence of 47.8% (197/412) internal parasitic infestation was assessed. Statistically significant difference at p<0.05 was noted in the prevalence of internal parasites among the different species, length and weight of fish. However, the difference between sexes was not statistically significant at p>0.05, but the prevalence was a bit higher in females (48.31%) than males (47.44%). Prevalence of internal parasites was higher in Clarias gariepinus (91.7%) followed by Oreochromis niloticus (50.22%), and Cyprinus carpio (15.6%) species. Six parasite species: three nematodes (Contracecum spp., Camallanus spp., Eustrongylides spp.); one trematode (Clinostomum spp.) and two cestodes (Ligula intestinalis, Proteocephalus spp.) were identified from the body cavities and gastrointestinal tracts of fishes. In conclusion, the prevalence of internal parasitic infestations was very high and the study determined six parasitic species present in fish, which were not previously examined in this Lake.