Pesticides include all xenobiotics which are used to kill another form of life, including insects (insecticides), small rodents (rodenticides), or even vegetation (herbicides). Organophosphate (OP) pesticides are broadly used for pest control due to their low persistence in the environment, broad spectrum and relatively low cost. The widespread use of organophosphates has stimulated research into the possible environmental effects related with health hazards and reproductive potential of organisms. Methyl parathion (MP) is an organophosphate pesticide used in agriculture although quite often illegally used indoors to control insects. Methyl parathion is metabolised to paraoxons and other metabolites which persists in the body of organisms including human beings for longer periods of time and are known to be more toxic than methyl parathion. Thus the present study is aimed to investigate the toxic effects of MP on hormonal profile (Testosterone, FSH, LH), biochemical profile (Total protein, cholesterol, ascorbic acid) and sperm parameters (Sperm abnormality, sperm count, sperm motility) in male albino mice. Animals were divided into four groups of six animals each. Group I animals were administered distilled water and served as control group. Group II and III animals were treated with acute doses of 1mg/kg body weight and 3mg/kg body weight of MP intraperitoneally. Group IV animals were given chronic dose of 0.05mg/kg body weight of MP intraperitoneally. Animals belonging to group I, II and III were sacrificed on 7, 14, 21 and 28 days post treatment. Animals of group IV were autopsied at 28 days post treatment. A marked statistically significant (p<0.005) reduction in serum level of testosterone, ascorbic acid, sperm count and sperm motility in MP exposed mice were noticed from 1st interval of autopsy to last interval in comparison to control animals. Whereas, a statistically significant increase in levels of FSH, LH, total protein, cholesterol, sperm abnormality were observed in MP treated groups as compared to control groups till the end of the experiment. When a comparison were made among treated groups I and IV, significant variations (p<0.05) were observed in all parameters. During the application of ANOVA, no significant difference (p>0.05) has been observed in hormonal profile and total cholesterol among treated groups i.e. group II and III. But when duration of treatment was considered, statistically significant (p<0.05) results were seen among treated groups. Hence, the present study indicates that MP induces severe testicular damage and results in reduction in sperm count, sperm motility and thus affect fertility. These findings were also supported by histopathological work on testes. Therefore, it can be concluded that MP has a profound effect on male reproductive system.