Purpose The purpose of this study was to develop and validate a tool to evaluate slow nursing performance for older adults in long-term care hospitals. Methods The search period was set from March 2013, when the term "slow nursing" was first used in the literature, to October 2021. A slow nursing tool was developed in two phases: development and verification. In the tool development phase, 29 items were developed through an extensive literature review and in-depth interviews with seven long-term care hospital nurses. Construct validity testing was performed by a 10-member expert panel, and a pilot survey was conducted on long-term care hospital nurses. In the tool validation phase, the construct validity, criterion validity, and reliability of the tool were tested by applying it to 181 nurses in long-term care hospitals . Results The final tool comprised five factors and 23 items, with an overall explanatory power of 56.8%. Construct validity was examined using confirmatory factor analysis, and the model fit was good. Known-group validity was established by the observation of a significant difference in the slow nursing score between intensive care unit and long-term care hospital nurses, and criterion validity was established by a significant correlation between the slow nursing and person-centered assessment scores. Internal consistency reliability was shown by a Cronbach's ⍺ coefficient of .781. Conclusion The concept of slow nursing has been clarified, improving the understanding and implementation of slow nursing care by nurses in long-term care hospitals. The Slow Nursing Tool for Long-term Care Hospital Nurses (SNT-LCHN) is expected to increase interest in and contribute to the effectiveness of slow nursing practices. It will serve as a valuable tool for improving nursing performance in these settings.