Abstract Aims Predictors of true degenerative mitral stenosis (MS) in patients with aortic stenosis who underwent transcatheter aortic valve implantation (TAVI) remain unknown. This study aimed to investigate the predictors and prognostic value of true degenerative MS in this population. Methods and results We retrospectively reviewed the records of 760 consecutive patients who underwent TAVI. The mitral valve area (MVA) was assessed using transthoracic echocardiography, and mitral valve calcification was assessed using multi-detector computed tomography. MS was defined as an MVA of ≤2.0 cm², and true MS was defined as moderate or severe MS following TAVI. In our TAVI cohort, we identified 72 (9.5%) patients with degenerative MS. Among these, true MS was observed in 38 (52.7%) patients. Echocardiographic data showed that the true MS group had a significantly lower MVA and higher trans-mitral gradient. The severity of mitral annular calcification was not significantly different between the two groups; however, the true MS group had significantly more posterior mitral leaflet (PML) and anterior mitral leaflet (AML) calcification. Multivariable logistic regression analysis showed that AML calcification was the independent predictor of true MS (adjusted OR, 9.23; 95% CI 2.84‒29.9). True MS was independently associated with poor prognosis (adjusted HR, 2.76; 95% CI 1.09‒6.98). Conclusions Approximately half of patients with concomitant degenerative MS who underwent TAVI had true MS, which was associated with a poor prognosis. Computed tomographic analysis of AML calcification was useful for predicting true MS.