Abstract Background: Nanotechnology is a rapidly developing science, and the nanoparticles (NPs) application invaded several fields. However, safety of these NPs is still a subject of debate and there are raising concerns about their harmful environmental and health effects. The aim of the current study was to investigate the potential toxicity of ZnO- NPs on cellular morphology and function of testis in albino rat with reference to the possible protective role of vitamin E (Vit E). Methods: Fifty adult male albino rats were categorized equally into 5 groups.G1, control, G2, ZnO-NPs-intoxicated, G3, Vit E-administered, G4, Vit E + ZnO-co-administered and G5, recovery group. ZnO- NPs with a crystalline size of < 50 nm were administered orally for 5 consecutive days. Vit E was orally- administered for two consecutive weeks, one week before the start of the experiment. Histological, histomorphometric, immunohistochemical, molecular and biochemical markers were investigated to explore the protective extent of Vit E against ZnO-NPs- induced cyto-and genotoxicity in testis. Results: ZnO-NPs were incorporated by Leydig cells, Sertoli cells and other spermatogenic cells resulting in structural and functional alterations in testis via the induction of apoptosis. Damaged Leydig, Sertoli and spermatogenic cells, vacuolated interstitial tissue, reduced tubular diameter, increased collagen deposition in the extracellular matrix (ECM), reduced PCNA immunoexpression, increased DNA damage and decreased levels of testosteron were recorded. Co-administration of Vit E normalized the picture to a large extent. Conclusion: The recorded results confirmed the potential of ZnO- NPs to induce apoptosis in testicular cells with impairment for spermatogenesis and consequently male fertility. Vitamin E played a pivotal role in protecting the testicular tissue of ratagainst the toxicity of ZnO- NPs.