RESILIA tissue expected to prevent structural valve deterioration owing to calcification on leaflets was firstly mounted in a mitral bioprosthesis, named MITRIS RESILIA mitral valve (MITRIS). MITRIS has softer cuff than Magna Mitral Ease and stent posts that deflect to prevent suture looping. A 77-year-old man, having a history of long-standing atrial fibrillation, presented with dyspnea on effort. An echocardiography suggested atrial functional MR. We successfully replaced mitral valve using a 27-mm MITRIS, and his postoperative course was uneventful with good hemodynamics. MITRIS may have advantages for implantability and durability, making it a promising prosthesis for patients requiring mitral surgery.