Background: Owing to their special properties, nowadays, NANOPARTICLES are extensively employed in most industries.Immediate effect, greater stability, and antimicrobial properties are among other significant and special factors of SILVER NANOPARTICLES causing these NANOPARTICLES to be utilized in most industries, including industries manufacturing medical equipment as well as household appliances.Studies have been undertaken since a few years ago to explore the detrimental effects of NANOPARTICLES on humans and such studies are being conducted increasingly.The present research was aimed at examining harms caused by SILVER NANOPARTICLES to male sex glands and sex hormones in Wistar rats.Materials and Methods: 75 male rats of approximately one month of age were organized in five groups of 15 rats (1 control group and 4 experimental groups). The rats in the experimental groups were fed SILVER NANOPARTICLES with concentrations of 25, 50, 100, and 200 mg/kg.After spermatogenesis (35 days), samples of blood were taken from the rats so that testosterone, LH, and FSH may be analyzed. Afterwards, the rats were dissected.Results: In general, the results obtained demonstrate a significant reduction in the number of Leydig cells in the experimental groups compared to the control one. Too, the results suggest a reduction in testosterone and a rise in LH, particularly, such a reduction and rise are significant in high doses (p<0.05); however, FSH showed no significant reduction.Conclusion: On the whole the results demonstrated that SILVER NANOPARTICLES disturb the functioning of sex hormones and disrupt the number of Leydig cells. This may affect the fertility potential in the laboratory animal.