The article presents the results of a study of sulfate reduction in the water and sediments of a small freshwater Lake Beloye (Konoshsky district, Arkhangelsk region)for the period from 2009 to 2017. The lake water belongs to the bicarbonate type of the calcium group according to Alekin’s classification. In winter, anoxic conditions were observed in the water of Lake Beloye in all years of the study, up to total oxygen depletion throughout the water column. The slightly elevated concentrations of sulfates in the lake water (up to 30 mg/l) in winter are due to the inflow of water draining the underlying sulfate rocks. This situation affected the process of sulfate reduction both in the water and in sediments of the lake. Sulfate reduction indices showed interseasonal and interannual variations. The highest recorded concentration of hydrogen sulfide in water during the ice-covered period was 405 μg/l (the maximum permissible concentration for fisheries reservoirs being 5 μg/l), and the highest amount of reduced sulfur compounds (hydrogen sulfide derivatives) in sediments was 7.33 % (based on sediment dry matter) or 73 % of the total sulfur. No hydrogen sulfide was detected in water during the summer due to aeration of the water column of this shallow lake. The activity of sulfate reduction in Lake Beloye is also indicated by the consumption of organic carbon, which amounted to an average of 1.42 % for the formation of reduced sulfur compounds versus 0.14 % consumption for iron reduction.