Background: One of the most essential and commonly utilized nanoparticles is zinc oxide nanoparticles (ZnO-NPs). They are widely used in commercial items such as sunscreens and daily-care products, as well as in the food industry as a food additive and in food packaging because of their antibacterial and fungicidal properties. Aim: The study aimed to evaluate the subacute toxic effects of different doses of ZnO-NPs on the kidneys of adult male albino rats. Methods: Forty adult male albino rats were divided into four groups (10 rats per group); Group I served as the control (Negative control), Group II ZnO-NPs treated group (10mg/kg/day), Group III ZnO-NPs treated group (100mg/kg/day) and Group IV ZnO-NPs treated group (200mg/kg/day) for 28 days orally. The levels of serum urea, creatinine, uric acid, and zinc were estimated. Furthermore, oxidative stress markers in kidney tissue, including malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione peroxidase (GPx) were estimated. Histopathological examination of the kidney tissues by light microscope was performed. Results: Oral ZnO-NPs induced a significant increase in serum creatinine, urea, uric acid, and zinc in a dose-dependent manner as the higher the dose the more significant toxicity. Zinc oxide nanoparticles induced a significant elevation of MDA and a significant decrease in the antioxidant enzymes SOD and GPx in kidney tissue also in a dose-dependent manner as toxicity is more evident in the high doses. Also, significant histopathological changes were detected in the kidney tissues. Conclusion: It can be concluded that subacute oral administration of ZnO-NPs induces nephrotoxic effects in a dose-dependent manner. The present study recommends that full attention must be given to evaluating the safety and toxicological issues of nanoparticles on the tissue, cells, and macromolecule of the human body.