The indications for a concomitant mitral valve (MV) procedure remain controversial for patients with hypertrophic obstructive cardiomyopathy (HOCM). According to previous studies, a concomitant MV surgery was required in 11-20% of inpatient operations. Thus, we aimed to study the outcomes of an extended Morrow procedure without a concomitant MV procedure for HOCM patients who had no intrinsic abnormalities of the MV apparatus. We retrospectively reviewed 232 consecutive HOCM patients who underwent extended Morrow procedures from January 2010 to October 2014. Only 10 (4.31%) patients with intrinsic MV diseases underwent concomitant MV procedures. Of the 232 patients, 230 had no to mild mitral regurgitation (MR) postoperatively. We separated the 232 patients into two groups according to preoperative MR degree. One group is mild MR, and the other is moderate or severe MR. The three-month, one-year, and three-year composite end-point event-free survival rates had no difference between two groups (p = 0.820). When we separated the patients to postoperative no or trace MR group and mild MR group, there was also no difference on survival rates (p = 0.830). In conclusion, concomitant mitral valve procedures are not necessary for HOCM patients with MR caused by systolic anterior motion, even moderate to severe extent.