Introduction: Diabetes mellitus is a major chronic metabolic disorder that induces memory and learning impairment. Herein, we investigated the protective effects of cerium oxide nanoparticles (CeO2) against streptozotocin (STZ)-induced memory impairment and antioxidant capacity in the diabetic rats. Methods: Adult male Wistar rats were assigned into the control, STZ, CeO2 and STZ plus CeO2 groups. Diabetes was induced using STZ and next CeNPs (60mg/kg) was administered for 14 constitutive days. The day after the last administration, spatial memory was assessed using the Morris water maze (MWM). Ultimately, the level of total antioxidant capacity (TAC) was investigated. Results: Our results showed that STZ significantly decreased the spatial memory and CeO2 could compensate for these changes. Furthermore, TAC increased following administration of CeO2 in the diabetic rats. Conclusion: The results of this study suggest that CeO2 seems to be able to improve STZ-induced neurotoxicity in the rats.