Background: Diagnosis and screening of frailty, a condition characterized by an increased vulnerability to adverse outcomes of COVID-19, has emerged as an essential clinical tool which is strongly recommended by healthcare providers concerned with hospitalized elderly population. The data showing the role of frailty in patients infected with COVID-19 is needed. Methods: This was a nationwide cohort study conducted at all hospitals in Turkey. All COVID-19 hospitalized patients (≥ 65 years) were included. Patients who were alive and not discharged up to July 20, 2020, were excluded. The frailty was assessed by using the "Hospital Frailty Risk Score" (HFRS). Patients were classified into three risk groups of frailty based on previously validated cut points as low (< 5 points), intermediate (5-15 points), and high (> 15 points). Additionally, patients who had the HFRS of ≥5 were defined as frail. The primary outcome was in-hospital mortality rates by frailty group.