Zooplanktons is very important group of living organisms, as they are the basis for food web in aquatic ecosystems. Among zooplanktons, cladocerans and copepods play a key role in the freshwater food chains. They transfer energy from microalgae to the higher trophic levels by being eaten as a food through various aquatic organisms. These creatures contain a valuable source of protein, amino acids, lipid, fatty acids, vitamins and enzymes. It has been demonstrated that several environmental factors such as temperature, depth, salinity, geographical location, season, food availability, and starvation could affect the fatty acids profile of zooplankton. In addition, it should be noted that the nutritional values, particularly fatty acids content, of mixed zooplankton strongly influences by the proportion of different zooplankton species in collected sample. Although there are many report on fatty acid composition of different zooplankton groups from separated geographical location information on fatty acid composition of mixed zooplankton from Iranian aquatic ecosystems are scarce. The purpose of this study was to provide basic information on fatty acid composition of mixed freshwater zooplankton from Hanna wetland situated at Eastern part of Isfahan province, Iran during different seasons. Furthermore, we investigated the effects of water quality and zooplankton community structure, mainly proportion of the individual constituents on fatty acid composition. In order to study the suitability of freshwater zooplankton of Hanna wetland, Isfahan, Iran for aquaculture purposes, determination of fatty acid composition of mixed zooplankton samples collected from the lake was carried out at in the middle of each season for a one-year period from May 2007 to February 2008. The samples were collected by vertical haul using plankton net (140 ?m). The total density of cladocerans was the highest in spring (%77.19) including three species of Daphnia longispina , D. dubia and D. pulex. The identified copepod species were all belong to cyclopoids, with the highest density observed in fall (%98.46). Fatty acid composition significantly (P 0.05) varied in relation to the seasonal changes of zooplankton community. The content of saturated fatty acids (SFA), mono unsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA) ranged from 27.79 -32.09 %, 39.18 -43.03%, 13.61-25.36 % of total fatty acids, respectively. Results showed that ratios of n-3:n-6 were 0.70:1, 2.53:1,1.89:1, and 1.73:1 in spring, summer, fall and winter respectively.