Increasing concern has been expressed about the declining sperm count of humans and the potential environmental effects of both synthetic and natural estrogenic endocrine disruptors (EEDs) on human reproductive health in the last few decades. However, due to paucity of knowledge, we evaluate the chronic reproductive toxicity of sesame phytoestrogenic lignans on the male Sprague Dawley (SD) rats' testis. Thirty adult male SD rats weighing 150-200g were divided into three groups. Two treated groups received a daily dose of aqueous leaves extract of Sesamum radiatum at 14.0 mg/kg bw and 28.0mg /kg bw respectively via gastric gavage, while equal volume of normal saline was administered to the control group for six weeks. Seminal analysis and hormonal assay study were analyzed using SPSS software and P< 0.05 was considered statistically significant. The results showed significant (P< 0.05) body weight gains observed in all the animals with significant (P< 0.05) weight increase in their raw testicular weights compared to control. The relative testicular weight per 100g bw was significantly (P< 0.05) higher in control than treated. However, theweight gain was dose related with a reversal in their relative testicular weight. The cauda sperm count including the motility and morphology of the treated were significantly (P< 0.05) higher than control in a dose related manner. In addition, significant (P > 0.05) increases in testosterone and a significant decrease in FSH in the high dose (treated) compared to control. Sesame phytoestrogenic lignans improves spermatozoa quality in a dose related manner.