Zinc oxide nanoparticles are incorporated into cosmetics and sunscreens and are widely used in biomedical applications and the food industry. The increasing use of zinc oxide nanoparticles raises concerns about their safety. The aim of the study was to assess the effects of zinc oxide nanoparticles on oxidative and genotoxic parameters in the thyroid gland and liver of adult albino rats.Oxidative stress parameters and genotoxicity were determined. Histopathological examination of both organs was undertaken. A significant reduction in triiodo thyronine, thyroxine and thyroid-stimulating hormone was noted, whereas aspartate aminotransferase and alanine aminotransferase levels were significantly elevated.