OBJECTIVES: This study sought to examine the prevalence of mitral stenosis (MS) and its impact on in-hospital and 1-year clinical outcomes among patients undergoing transcatheter aortic valve replacement (TAVR). BACKGROUND: Patients with coexisting severe aortic stenosis and MS are increasingly being considered for TAVR. METHODS: The study cohort included 44,755 patients (age ≥18 years) who underwent TAVR during November 1, 2011, to September 30, 2015, and were registered in Society of Thoracic Surgeons/American College of Cardiology Transcatheter Valve Therapies (TVT) Registry. One-year outcomes were assessed by linking TVT registry data of this cohort to patient-specific Centers for Medicare & Medicaid Services administrative claims data (n = 31,453). The primary outcome was the composite of death, stroke, heart failure-related hospitalization, and mitral valve intervention at 1 year. RESULTS: MS was present in 11.6% of cohort (mean age, 82 years; 52% males), being severe in 2.7%. Severe MS was associated with higher in-hospital mortality rates (5.6% vs. 3.9% for nonsevere MS and 4.1% for no MS; p = 0.02). In contrast to those without MS, severe MS group had significantly higher risk for the primary outcome, mortality (1 year), and heart failure-related hospitalization (1 year) (adjusted hazard ratio: 1.2 [95% confidence interval (CI): 1.1 to 1.4], 1.2 [95% CI: 1.0 to 1.4], and 1.3 [95% CI: 1.1 to 1.5], respectively; p < 0.05 for all). CONCLUSIONS: Approximately one-tenth of patients undergoing TAVR have concomitant MS. Severe MS is an independent predictor of 1-year adverse clinical outcomes following TAVR. The higher risk for long-term adverse events must be considered when evaluating patients with combined aortic stenosis and MS for TAVR.