Endosulfan is a pesticide of organochlorine group, It is used to control pests on fruits, vegetables, and tea and on non food crops such as tobacco & cotton. Government of Kerala (India) banned this pesticide due to its hazardous effect on reproductive health in cashew nut workers of Kassargod district. So, an intensive study was required for it.In the present investigation, the dose of 3 mg/Kg b.w of Endosulfan was continuously administered to male mice for 35 days. The mice were sacrificed on 35th day to observe the sperm morphology and level of Testosterone and Luteinizing hormone (LH) in the serum.After treatment, major changes were observed with loss of sperm tail, degenerated acrosome, coiled tail and declination in the level of Testosterone and inclination in the level of LH were observed which signify the testicular dysfunctions and finally causes infertility in male mice.