Background: Frailty is associated with increased morbidity and mortality and frail patients may have reduced ability to tolerate severe vital sign derangement such as estimated by a high National Early Warning Score (NEWS). The clinical impact of frailty among patients that develop high NEWS during hospital admissions is sparsely studied. The aim of this study was to investigate the association between clinical frailty and admission to intensive care unit (ICU) among these patients. Methods: We conducted a prospective observational study from November 2017 to January 2018. We included adult patients admitted to general wards that during hospitalization developed severe vital sign derangement defined as NEWS ≥7. Patients were without treatment restrictions at inclusion. Primary exposure was frailty as assessed by the Clinical Frailty Scale. Primary outcome was ICU admission within 90 days, which was analyzed using multivariate logistic regression. Results: We included 109 patients with NEWS ≥7, of which 61 patients (56%) were frail. Ten of the 61 frail patients (16%) were admitted to ICU compared to 9 of the 48 non-frail patients (19%), adjusted odds ratio (aOR) 0.92 (95% CI 0.32-2.62). Frail patients were more likely to have new treatment restrictions (aOR 2.91; 95% CI 1.26-6.71). Their aOR for mortality was 1.95 (95% CI 0.84-4.55). Conclusion: Frail patients with severe vital sign derangement during acute hospital admissions were not more likely to be admitted to ICU nor was mortality higher. Treatment restrictions were more frequent among frail patients after vital sign derangements developed.