Background and aim: Surgical repair of secondary mitral regurgitation is still controversial especially when the cardiac function is reduced. The purpose of this study was to retrospectively investigate the operative and long-term results of mitral valve surgery for secondary mitral valve regurgitation with poor cardiac function. Risk factors for long-term mortality were also investigated. Methods Patients with preoperative echocardiographic left ventricular ejection fraction ≤30% who underwent mitral valve surgery due to secondary mitral regurgitation comprised the study group. Cardiac function and valve regurgitation was assessed with echocardiogram using modifiled Simpson’s method and color-flow Doppler. Peri-operative results and long-term survival were investigated. Results Sixty-nine patients (mean age 65.5 years, 58 males) with secondary mitral regurgitation and poor left ventricular function comprised the study group, and their early results were investigated; long-term results were evaluated in 66 cases. There were no operative/in-hospital deaths. Postoperative echocardiograms showed significantly improved mitral regurgitation, from moderate to severe to less than trivial (p<0.001), although poor left ventricular function remained. Actual 1-, 3-, and 5-year survival rates were 90.5%, 76.5%, and 63.4%, respectively. The 1-, 3-, and 5-year re-admission-free rates due to heart failure were 74.6%, 61.6%, and 55.3%, respectively. Patients with clinical frailty scale scores ≥4 had a worse prognosis than patients with clinical frailty scale scores <4 (log-rank p=0.046). Conclusions Open mitral valve surgery could be appropriate for secondary mitral valve regurgitation with poor cardiac function, however, operative indications should be considered carefully in patients with high clinical frailty scale scores.