Background: Psoas muscle mass is a recently featured index of sarcopenia, which has a negative prognostic impact in patients with a variety of diseases. We investigated the prognostic impact of baseline psoas muscle mass in patients receiving a trans-catheter aortic valve replacement (TAVR). Methods: Patients who received TAVR at our center between 2015 and 2022 were included. Patients received computer tomography imaging upon admission as an institutional protocol, and psoas muscle mass was measured, which was indexed by body surface area. Patients were followed for four years or until January 2023. The prognostic impact of psoas muscle mass index on 4-year mortality following index discharge was evaluated. Results: A total of 322 patients (85 years, 95 male) were included. Median psoas muscle mass index at baseline was 10.9 (9.0, 13.5) × 10 cm3/m2. A lower psoas muscle mass index tended to be associated with several index of malnutrition and sarcopenia. A psoas muscle mass index was independently associated with 4-year mortality with an adjusted hazard ratio of 0.88 (95% confidence interval 0.79–0.99,p= 0.044). Patients with lower psoas muscle mass index (below the statistically calculated cutoff of 10.7 × 10 cm3/m2, N = 152) had significantly higher cumulative 4-year mortality compared with others (32% versus 13%,p= 0.008). Conclusions: A lower psoas muscle mass index, which is a recently featured objective marker of sarcopenia, was associated with mid-term mortality following TAVR in the elderly cohort with severe aortic stenosis. The measurement of psoas muscle mass index prior to TAVR could have clinical implications for shared decision-making among patients, their relatives, and clinicians.