SUMMARY: This study aimed at clarifying the impact of long-term prenatal and postnatal exposure to exogenous progesterone on sperm production and function, relative sex organs weights, and the levels of the relevant hormones in rats. Sixty male Wistar rats were included and classified into three groups (n=20 in each). A test I group had mature rats born to dams treated with progesterone prenatally. A test II group included rats exposed to progesterone during prenatal as well as postnatal periods, and a control group had rats treated with a placebo (olive oil). The test groups revealed a significant reduction in sperm count, motility, and viability with higher abnormal forms than the control group (P< 0.05). Similarly, the test groups revealed significantly lower serum testosterone and higher FSH and LH levels (P< 0.001). Interestingly, the test II group showed pronounced sperm abnormalities, an alarming decrease in sperm viability and motility, and a significant accretion in the relative testicular weight compared to the test I group (p <0.001). Long-term (prenatal and early postnatal) treatment with synthetic progesterone hurts sperm quantity and quality, adversely affecting future male fertility.