Mercury accumulation in different tissues of Cyprinus carpio was measured after exposing the fish to 25 and 50 ppb mercury for 15 and 30 days. At the end of experiments, gill, liver, spleen and brain tissues of fish were dissected separately. Dissected tissue samples were prepared with wet digestion for mercury analysis. Mercury concentration of samples was determined by cold vapor atomic absorption spectrophotometry. For all the tissues analyzed, mercury accumulation level displayed an increase, depending on the medium mercury content and exposure period. When compared to the other tissues, a more evident increase was reported in the mercury level of spleen tissue, especially in the 50 ppb medium mercury content. Among all the tissues analyzed, mercury level in the liver tissue is the lowest one among the other tissues.