This study was conducted to evaluate the antifertility potential of Thevetia peruviana (Apocynaceae) in male albino rats with their phytochemical evaluations. Phytochemical examination showed that plant is rich in active constituents, i.e. α-amyrin acetate, lupeol acetate, α-amyrin, β-amyrin, lupeol and thevetigenin. T. peruviana stem bark methanol extract (TPMtE) administered orally to male rats at the dose level of 100 mg/rat/day did not cause any significant reduction in body weight, while the weight of reproductive organs reduced significantly. A significant fall in the total protein and sialic acid content of the testes, epididymides, seminal vesicle and ventral prostate, as well as in the glycogen content of testes was also observed; however, cholesterol was increased significantly. TPMtE also caused a decline in spermatogenic elements, i.e. preleptotene and pachytene spermatocytes, secondary spermatocytes, round spermatids and mature Leydig cells. At this dose level Leydig cell nuclear diameter, seminiferous tubular diameter and Sertoli area were significantly reduced (p < 0.001). The reduction in sperm density and motility resulted in 18% residual fertility. In conclusion, T. peruviana inhibited spermatogenesis in rats, indicating the possibility of developing a herbal male contraceptive.