<p>The extensive use of pesticides for controlling insects has been widely used in agricultural activities. However, the indiscriminate use of the pesticides has inflicted serious harmful problems to humans in the ecosystem. Our study aims to evaluating the capacity of Armillaria tabescens to remove the chemical oxygen demand (COD) and biochemical oxygen demand (BOD5) at different concentration of malathion insecticide (50, 100 and 150 ppm) under agitated (130 rpm) submerged culture conditions at 27 0C after 8 and 15 days. According to our results, A. tabescens has achieved COD reduction as 52.39, 27.24, and 38.30% at concentration of 50, 100 and 150 ppm respectively on 15 days. The BOD5 reduction rates were found as 78.2, 74.76 and 81.26% at 50, 100 and 150 ppm concentration respectively at the end of the 15th days. At the end of this time period, the dried biomass of A. tabescens was weighted and we have suggested that malathion in medium reduced the biomass production compared the control group (Sabouraud dextrose broth + A. tabescens). Our experiments have focused that; A. tabescens could be an alternative and useful fungus for bioremediation of wastewater containing malathion insecticide.</p>