Objective: To investigate the effects of prenatal progesterone exposure of male rats on testicular morphometry and histology. Methods: Twenty male Wizard rats b to dams treated with hydroxyprogesterone hexanoate (HPH) during the first 2 weeks of gestation were employed to evaluate the effects of HPH on testicular morphometry, histology and cells quantities. Twenty male rats b to untreated dams were used as control. The rats were kept until they reached 90 days old, sacrificed, testes dissected, weighed and their dimensions recorded. Histological sections were prepared and stained with H&E. The diameter of the seminiferous tubule (ST), height of germinal epithelium, and thickness of the interstitial space (IS) were measured microscopically. Furthermore testicular cells were quantified. Results: The results showed that experimental rats had significantly (P < 0.001) different testicular morphometry, histology and cells quantities compared to the control. The histological sections taken from testes of experiment group showed ST with unusual configuration, detached and/or folded basal lamina, thin germinal layer, wide IS with few LC, Sertoli cells experienced varying degrees of apoptosis and the lumen of ST contained cells debris and very rare few sperms. Conclusions: Prenatal HPH exposure of male rats adversely affects their testicular morphometry and histological structure and presumably has crucial negative effects on their future fecundity.