Skeletal muscle mass (SMM) as calculated by computed tomography (CT) is a predictor of all-cause mortality after transcatheter aortic valve replacement (TAVR), but it remains unclear whether using CT-determined density of skeletal muscle has additive prognostic value. We utilized the Japanese multicenter registry data of 1375 patients who underwent CT prior to TAVR. Sarcopenia status was defined by the CT-derived SMM index (threshold: men, 55.4 cm²/m²; women, 38.9 cm²/m²). The threshold for high and low CT density was based on the median value of the entire cohort (men: 33.4 HU; women: 29.5 HU). Sarcopenia was observed in 802 patients (58.3%) overall. Patients were categorized into non-sarcopenia and high-CT density (n = 298), non-sarcopenia and low-CT density (n = 275), sarcopenia and high-CT density (n = 399), and sarcopenia and low-CT density (n = 403) groups, and procedural outcomes and mortality compared. The cumulative 3-year mortality rates in these groups were 18%, 27%, 24%, and 32%, respectively. Cox-regression multivariate analysis revealed that low-CT density (compared with high-CT density) and sarcopenia and low-CT density (compared with non-sarcopenia and high-CT density as reference) increased mortality after TAVR (hazard ratios [HR]: 1.35 and 1.43, 95% confidence intervals [Cis]: 1.06–1.72 and 1.00–2.08, p = 0.01, and 0.049, respectively). However, sarcopenia alone was not related to an increased risk of mortality (HR 1.30, 95% CI 0.99–1.69, p = 0.52). In conclusion, CT density-based skeletal muscle quality assessment combined with the SMM index improves prediction of adverse outcomes after TAVR.