Warfarin is commonly used as an anticoagulant after mitral valvuloplasty （MVP）. The efficacy of warfarin varies widely from patient to patient, and sometimes optimal prolongation of PT-INR cannot be achieved even with high doses of warfarin. In the present case, PT-INR was not prolonged to the target value even after 9 mg of warfarin and 300 mg of Bucolome due to warfarin resistance, and a direct oral anticoagulant （DOAC） was administered as an alternative drug. The patient was a 57-year-old male who became aware of easy fatigue and visited a medical institution for a heart murmur. Transthoracic echocardiography revealed a severe mitral regurgitation （MR） due to thickening of the anterior mitral leaflet and prolapse of the posterior leaflet. Postoperative echocardiography showed no MR, good valve mobility, an effective valve opening area of 2.0 cm2, and an improved blood flow velocity of 0.9 m/s. Warfarin was started on the day after surgery, but the dose was gradually increased because PT-INR was not prolonged. The PT-INR was less than 1 even with 6 mg of warfarin, and the patient was started on Bucolome. The PT-INR was 1.27 after 9 mg of warfarin and 300 mg of Bucolome. The patient was diagnosed as warfarin-resistance and was discharged from the hospital after warfarin was discontinued and dabigatran 300 mg was administered. Dabigatran was discontinued at 3 months after surgery without any embolism or bleeding complications. In some cases, PT-INR prolongation may not be achieved due to warfarin resistance caused by genetic polymorphisms, and in such cases, DOACs can be used as anticoagulants after mitral valvuloplasty.