A crosssectional study on parasitic infections of fish was conducted from December 2011 to May 2012 at Lake Tana to identify parasites of important fish species. The fish were sampled from three different sites (South, East and West) of the lake and the sampling were taken at morning time randomly on different boats and transported to the recommended laboratory by cooler jar filled with water from the lake itself From the total of 1197 samples 924 (77.2%) were infected, Labeobarbus species (n = 450, 52. 13%), Nile tilapia (Oreochromis niloticus) (n = 477, 78.53%) and catfish (Clarias gariepinus) (n = 300, 18.63%) were examined using standard laboratory techniques. From total number of fishs examined 450 (43.9%) were males and 7 47 (71. 8%) females. Accordingly, the major parasite noticed during investigation include the dominant encysted pleurocercoid with prevalence rate of (28.9%) followed by the monogenean Clinostomum species (18.3%) and Contracaecum species larvae (17.8%). From all organs examined, skin was highly infested by eight different types of parasites (11. 75) and external crustacean, Dolops species (5.26%). The external protozoa (Trichodina species) ( 4. 5%) was found only in southern part of the Lake. Fish from the three areas were infested with different parasite species and the southern partof the lake was found to harbour the highest prevalence (150.4%) of parasitic infestations. The larval nematode Contracaecum species had highest mean intensity of 3 in the South, 4 in West and 5 in East and with mean abundance of 0.15, 0.63 and 0.58, respectively. Further assessment of parasites in thier intermediate and final hosts like piscivorous birds as well as in humans is paramount important.