Zinc oxide (ZnO) nanoparticles have been used as a source of zinc, in food industry and are applied in cosmetic products, but their accumulation in the tissues causes a hazard toxic effect. Naringenin (Nar) is a member of flavanones groups that play an important role in body health in terms of antioxidant and anti-inflammatory. Aim: The aim of this study is to evaluate the possible structural changes that occur in the testicular tissue of adult albino rat after single injection of zinc oxide nanoparticles and to clarify possible protective role of Naringenin against this toxicity. Material and methods: 28 adult male albino rats have been used in this work. These animals were divided into three groups. Group Ia (Control -ve): Animals received no chemicals. Group Ib (control +ve) rats received oral Naringenin 20mg/kg once daily for two weeks. Group II (Treated group) received single intraperitoneal injection (IP) of Zno-NPs (700 mg/kg) (as a single toxic dose in the experiment). Group III (Protective group) rats received Zno NPs (as same previous dose and route) in addition to Naringenin (20mg/kg) orally once daily for 2 weeks. 24 hours after the last administration, rat were sacrificed, carful dissection was performed for gentle removal of both testicles from all groups then processed for light and electron microscopic studies, morphometric examination and statistical analysis. Epididymal sperm was collected for estimation of percentage of sperm Viability and abnormality. Results: By light microscopy, zinc oxide nanoparticles caused massive histopathological changes in rat testes in the form of disorganization of seminiferous tubules, thickening, detachment and separation of basement membranes, widening of interstitial tissues, thickening and congestion blood vessels and pyknosis of sertoli and germ cells. Ultrastructural results confirmed these histopathological changes and revealed the degeneration of Sertoli cells, all germ cells and interstitial cells as well. The statistical analysis of this study supported the results. Administration of Naringenin to treated group provided mild improvement to the testicular tissues against Zno-NPs toxicity. Conclusion: zinc oxide nanoparticles could result in hazards to the structure of testes. Fortunately co-administration of Naringenin is suggested to reduce such hazards.