Background and Aim of the Study: Negative impact of prosthesis-patient mismatch (PPM) on long term survival after valve replacement has been reported. However, the effect of PPM after bioprosthetic mitral valve replacement (MVR) has not yet been well examined. The purpose of this study was to investigate the effect of PPM on late outcomes after bioprosthetic MVR for mitral regurgitation (MR). Methods: A total of 181 patients underwent bioprosthetic MVR between April 2008 and December 2016. After excluding patients with mitral stenosis and those with incomplete data, 128 patients were included in the study. Postoperative transthoracic echocardiography was performed for all patients and the effective orifice area (EOA) was calculated using the pressure half-time method. The effective orifice area index (EOAI) was calculated by the formula: EOA/body surface area (BSA). PPM was defined as a postoperative EOAI ≤ 1.2 cm2/m2. The characteristics and outcomes were compared between the groups. Results: There were 34 patients (26.6%) with PPM and 94 patients (73.4%) without PPM. Although proportion of males and BSA were higher in the PPM group, valve size distributions were similar between the two groups. There were no significant differences in the in-hospital mortality and morbidities. Multivariable analysis showed that PPM was an independent predictor of late mortality (hazard ratio [HR] 3.38; 95% confidence interval [CI] 1.69-6.75; p = .001) and death from heart failure (HR 31.03, 95% CI 4.49-214.40, p < .001). Conclusions: PPM after MVR for MR was associated with long-term mortality and death from heart failure.