The present study investigated the histopathological effects of the phytopesticide Azadirachta indica on the seminal vesicles of adult male Odontopus varicornis. The 48-hour median lethal dose was determined to be approximately 0.05 ppm. Morphologically, the male reproductive system of O. varicornis consists of a pair of testes, vas deference, and seminal vesicles. In the adult male reproductive system, the seminal vesicle appears as a white, oval shaped body and is richly supplied with tracheoles. It lies in the posterior region of the abdomen, situated between the vas deferens and the ejaculatory duct. The posterior portion of the seminal vesicle connects directly to the median ejaculatory duct. Exposure to A. indica induced severe cellular damage within the seminal vesicles, characterized by the breakdown of epithelial cell walls, cytoplasmic vacuolization, nucleus pyknosis, lumen, and a marked reduction in secretory fluids, ultimately leading to insect sterility.