Older patients from long-term care hospitals (LTCHs) presenting to emergency departments (EDs) exhibit a higher prevalence of frailty than those from the community. However, no study has examined frailty in patients from LTCHs in the ED. This study compared frailty in older patients from LTCHs and the community. We retrospectively analyzed data from the EDs of three university hospitals between 1 August and 31 October 2023, involving 5908 patients (515 from LTCHs and 5393 from the community). The Korean version of the Clinical Frailty Scale (CFS-K) was used to assess individuals aged 65 and older. We compared clinical characteristics, frailty, length of stay (LOS), and diagnosis between patients from LTCHs (LTCH group) and the community (community group). Among ED patients, 55.0% and 35.2% in the LTCH and the community groups, respectively, were frail (p < 0.001). Of these, 71.7% in the LTCH group were hospitalized compared with 53.1% in the community group (p = 0.001). The odds ratio for in-hospital mortality was 4.910 (95% CI 1.458-16.534, p = 0.010) for frail LTCH patients and 3.748 (95% CI 2.599-5.405, p < 0.001) for frail community patients, compared to non-frail patients. Patients from LTCHs with frailty had higher hospital admission rates and increased in-hospital mortality compared to those in the community at the same frailty level. This study offers essential insights into the characteristics of older patients in LTCHs for healthcare administrators and medical staff worldwide.