Background: In Japan, the effects of reduced water, such as hydrogen-rich electrolyzed reduced water and natural reduced water, like Hita Tenryosui water®, have been examined. The purpose of the present study was to identify the role of natural reduced water in anxiety and blood biochemical analysis.Materials and methods: Natural reduced water and distilled water were administered to rats for 180 consecutive days, and their effect on anxiety-like behavior and depression was examined by using elevated plus maze, light/dark, forced swimming, and conditioned fear tests. Before and after administration of natural reduced or distilled water, we performed blood and urine analyses. Results: Natural reduced water exhibited anxiolytic-like effects in the conditioned fear and elevated plus maze tests. The mean levels of urinary 8-hydroxy-2′-deoxyguanosine (8-OHdG) in the natural reduced water were significantly lower than the distilled water group. Natural reduced water group also showed decrease in blood-urea nitrogen levels compared with the distilled water group. Conclusion: These results indicate that natural reduced water may decrease anxiety-related behaviors and prevent heightened oxidative stress.