Pyridaben is a pyridazinone derivative, which has been used as an acaricide and insecticide over the past decade throughout the world. Its adverse effect on the male reproductive system is not well established. In normal reproduction, the physiological levels of the gonadotropic as well as gonadal hormones are key factors; an increase in levels of reactive oxygen species (ROS) and nitric oxide stress (NOS) adversely influence reproduction. To study the effects of changes in these hormones and in levels of ROS and NOS after exposure to pyridaben, 80 adult and apparently healthy male Balb/C strain mice were used. The animals were allocated into three groups: controls, test group 1 and test group 2. Test groups 1 and 2 received the toxin at rates of 53 mg/kg body weight and 212 mg/kg body weight, respectively. The durations of the exposure for both groups were 10, 25 and 45 days. A significant decrease was seen in follicle-stimulating hormone (FSH) levels by days 10 (p < 0.05), 25 (p < 0.001) and 45 (p < 0.001) in the low-dose group; however, in the high-dose groups, the reductions in FSH levels 10, 25 and 45 days after exposure were highly significant (p < 0.001). In both the low- and high-dose groups, a highly significant (p < 0.001) decrease in the level of luteinizing hormone was observed. Levels of testosterone in the control and different test groups showed a significant difference; in the low-dose group, the difference was significant (p < 0.01) after 45 days of exposure, but in the high-dose group, it was significant (p < 0.01) after 25 days of exposure, whereas it was highly significant (p < 0.001) after 45 days of exposure. The levels of ROS and NOS increased in all test groups.