BACKGROUND: Most older people with disabilities or illnesses continue to use long-term care (LTC) services for the rest of their lives. However, disasters can cause a discontinuation of LTC services, which usually means tragic outcomes of affected persons. In view of the recent progression of population aging and the increase in natural disasters, this study focuses on the impact of disasters on older people's discontinuation of LTC services, and those more risk of such discontinuation than others. However, current evidence is scarce. METHODS: We conducted a retrospective cohort study with 259,081 subjects, 2,762 of whom had been affected by disaster and 256,319 who had not been affected during the 2018 Japan Floods. The sample in the three most disaster-affected prefectures was drawn from the Long-term Care Insurance Comprehensive Database and included older people certified with care-need level. The observation period was two months before the disaster and five months after it. We calculated the hazard ratio (HR) of municipality-certified subjects affected by the disaster versus those who were not. Subgroup analyses were conducted for categories of individual-, facility- and region-associated factors. RESULTS: Affected persons were twice as likely to discontinue LTC services than those who were not affected (adjusted HR, 2.06 95% CI, 1.91-2.23). 34% of affected persons whose facilities were closed discontinued their LTC services at five months after the disaster. A subgroup analysis showed that the risk of discontinuing LTC services for affected persons compared to those who were not affected in the relatively younger subgroup (age < 80: adjusted HR, 2.55; 95% CI, 2.20-2.96 vs. age ≥ 80 : 1.91; 1.75-2.10), and the subgroup requiring a lower level of care (low: 3.16; 2.74-3.66 vs. high: 1.71; 1.50-1.96) were more likely to discontinue than the older and higher care level subgroups. CONCLUSIONS: A natural disaster has a significant effect on the older people's discontinuation of LTC services. The discontinuations are supposedly caused by affected persons' death, hospitalization, forced relocation of individuals, or the service provider's incapacity. Accordingly, it is important to recognize the risk of disasters and take measures to avoid discontinuation to protect older persons' quality of life.