The occurrence of conflicting reports on the improvement of male reproductive function among humans fed diet containing the seed of Mucuna pruriens (MP) have raised a major concern in Nigeria. We assessed the effect of MP seed powder on the reproductive function in 32 adult male albino rats randomized to 4 groups of 8 rats each for 8 weeks. Group 1 (control) was given standard rat chow while groups 2, 3 and 4 were fed diets containing MP seed powder at 0.75 g, 1.5 g and 2.25 g respectively. Serum level of follicle stimulating hormone, testosterone, luteinizing hormone, oxidative stress markers in the testis, epididymal sperm quality and cytoarchitectural structure of the testis were monitored using standard methods. Significant improvements (p < 0.05) in the serum levels of all the hormones, testicular antioxidant defence, epididymal sperm quality without testicular degenerative changes were observed in group 2 compared to other groups. Oxidative stress, severe degenerative architectural lesions in the testis as well as significant reductions (p < 0.05) in epididymal sperm count, percentage motility and significant (p < 0.05) increased in abnormal sperm cells were observed in group 4. MP seed enhances reproductive function in male rats only at a dose level of 0.75g. A dose value higher than 0.75 g may be toxic to the male reproductive system. © 2019 Published by Elsevier Ltd.