Objective(s): pyriproxyfen as an insect growth regulator is widely used globally for pest management. There are reports on adverse effects of insecticides such as organ toxicity, endocrine disruptions, and teratogenicity in animals and humans. We aimed to investigate reproductive toxicity of pyriproxyfen in adult male mice. Materials and Methods: 48 male Swiss albino mice were divided into eight groups and received the different 1200, 600, 320, 200, 100, 40, 20, 0 mg/kg/day doses orally, and body weights were accessed for 28 consecutive days. In the end, mice were sacrificed, testes were dissected and weighed. Probable testicular tissue alterations were examined by histopathological studies. In addition, the diameter of seminiferous tubules and Leydig cells distribution were assessed in all experimental and control groups. Results: pyriproxyfen treatment caused significant (P<0. 05) reduction in body and organ weights in mice. However, the shrinkage and displacement of seminiferous tubules, reduced lumen diameter, and vacuolization occurred in seminiferous tubules in higher doses exposed animals in comparison to controls. The relative testis weights, mean diameter of seminiferous tubules, and Leydig cells distribution remained unchanged at low doses. Conclusion: These findings reveal that pyriproxyfen caused reduction in body weight gain as well as damage to the testicular architecture in mice and thus may potentially interfere with spermatogenesis. Findings in an outbred strain of mice can be extrapolated fairly reliably to the human model. The chemical can thus be further exploited to study its effects on impairment of fertility and as an endocrine disruptor.