Purpose: This study was done to evaluate the effects of a fluid intake intervention on increasing fluid intake and ameliorating dehydration status in elders admitted to long-term care hospitals. Methods: A nonequivalent control group, pretest and posttest design was used. The experimental group of 39 participants received the 4-week intervention while the control group of 38 participants received routine care. Outcome variables were daily fluid intake and physiological indexes such as blood urea nitrogen and creatinine ratio (BUN/Cr), urine specific gravity (USG), and urine color. Results: After the intervention to increase fluid intake, there were statistically significant increases in daily fluid intake, normal BUN/Cr, and USG in the experimental group. However, a statistically significant improvement in normal urine color was not found for either group. Conclusion: The findings of this study demonstrated that the fluid intake intervention improved hydration status of the experimental group participants. Consequently, it was confirmed that the intervention is considered to be effective in preventing dehydration which occurs frequently in older adults in long-term care facilities and, thus this intervention may contribute to preventing various health issues resulting from dehydration.