[en] When pesticides are present in high concentrations in the environment causing irreparable, metabolic, physiologic and structural damage on the organisms. Diazinon and Deltamethrin are of the most widely used agricultural pesticides in the northern Iran that can enter aquatic ecosystems. Anatropous fishes like Kutum have most reactions with pollutants because of their spawning in the first spring. Kutum is suitable species for toxicity testing in the southern coast of the Caspian Sea, due to the wide distribution. The aim of present study was to determine the effects of Nano-clay in reducing the fatality rate of diazinon and Deltamethrin on the Caspian Sea Kutum. 210 pcs kutum with a mean weight of 24 g were collected from fish stocks Syjval and after two weeks of adaptation in laboratory toxicity tests carried out for 96 hours. The results of this study showed that 500 mg / L clay is the greatest losses while 1000 mg / L Nano clay increased the death toll is likely to rise due to high water and mud contaminated fish is breathing difficulty.