This study presents the data on first years (2013–2015) of the Boguchany reservoir structural formation, along with evolution of the dominant zooplankton community in its the upper portion. The study has been conducted at six stations located on the 130 km stretch in the lower reaches of the Angara River (downstream from the Ust-Ilimsk Dam). Given that both the composition and structure of zooplankton in Boguchany Reservoir, which closes the Angara cascade of hydropower stations (Dams), experience the influences from the Irkutsk, Bratsk and Ust-Ilimsk Reservoirs they appear in many ways similar to the fauna of rotifers and crustacea from these reservoirs located in the upstream part. Baikal Lake endemic Epischura baikalensis, and dominant species of the Irkutsk Reservoir from Notholса and Euchlanis ligulata genera have been detected in the upper portion of the studied reservoir. During first years of reservoir filling, the zooplankton diversity didn’t change, amounting to 28–30 species. Its biomass and quantity is determined by the mass crustaceans typical for the Bratsk Reservoir: Cyclops kolensis, Daphnia galeata, Diaphanosoma brachyurum, and inhabitants of deep-water layers near the dam of the Ust-Ilimsk Reservoir: Cyclops abyssorum, Daphnia cristata, Daphnia longiremis, Heterocope appendiculata. As the Boguchany reservoir was filling with water, the river flow rates slowed down, and the temperature water decreased, while the depth of water increased, which created favorable environmental conditions for the limnofauna in the upper portion of the reservoir. For instance, in the third year (2015) of reservoir filling, when the reservoir water level reached the projected mark (208 m Baltic System), the quantity and biomass of the zooplankton had reached 57 600 specimen/m3 and 1050 mg/m3 , respectively, on the Edarma station located 100 km below the Ust-Ilimsk Dam, which is significantly higher than the levels observed in 2014 (13 000 specimen/m3 and 165 mg/m3 respectively).Keywords: Boguchany Reservoir, filling period, upper part of reservoir, formation, zooplankton community.