Due to the increasing use of nanoparticles in medical and industrial fields, concerns are growing about the toxicity of them to the body organs especially the reproductive system. In this review, the effect of metal/metal oxide nanoparticles on the mammalian reproductive system was discussed. Nanoparticles are typically toxic to both males and females, depending on their types, administration method, exposure duration, and surface modification. Regarding the embryo, it was also found that the effect of nanoparticles depends on the embryonic stage exposure during development. However, some nanoparticles, depending on the dose and time of administration, not only did not have toxic effects, but also strengthened the reproductive system and increased its efficiency. As the mode of interaction, penetration, and mechanism of nanoparticles action in the reproductive system is unclear, this review highlights the importance of additional tests in these cases.