Abstract Background Secondary mitral regurgitation (SMR) impacts outcomes in heart failure with reduced ejection fraction (HFrEF) but whether it is a specific therapeutic target in heart failure patients with preserved ejection fraction (HFpEF) is less clear. Purpose The aims of this study were to investigate whether surgical or trans-catheter intervention reduces SMR and improves outcomes compared to optimal medical therapy in HFpEF patients. Methods We retrospectively identified 120 HFpEF patients with moderate-to-severe or greater SMR from January 1, 2007, until December 31, 2017. Moderate-to-severe SMR was defined as an effective regurgitant orifice area of >0.3cm2, and/or a regurgitation volume of >45ml per beat. Those with primary mitral regurgitation, endocarditis, HFrEF, hypertrophic cardiomyopathy, congenital heart disease, and history of valve intervention were excluded. All-cause mortality was analyzed and correlated to clinical and echocardiographic characteristics. Amongst the 120 patients, 36 received surgical or trans-catheter procedure in addition to medical therapy (procedure group) and 84 patients received optimal medical therapy only (conservative treatment group). The median follow-up period was 864 (15–3553) days. Results Patients in the procedure group were younger (75±8 vs 81±10, P=0.0002) and with fewer comorbidities (Charlson Comorbidity Index 7.0±2.4 vs 8.0±2.0, P=0.022) compared to the conservative treatment group. In addition, the procedure group had larger left ventricular end-diastolic diameters and higher SMR volume at baseline. During follow-up, SMR decreased by ≥2 grades in 75% of patients (27/36) in the procedure group compared to 20% of patients (12/60) in the conservative treatment group. After adjusting for age and comorbidities, the procedure group showed better overall survival compared to the conservative treatment group (HR 0.37; 95% CI 0.17–0.80; P=0.011). On multivariate analysis for the different groups (procedure group vs. conservative treatment group) (HR 0.40; 95% CI 0.17–0.91; P=0.019), increasing Charlson Comorbidity Index (HR 1.16; 95% CI 1.02–1.32; P=0.028) and average mitral E/e' ratio (HR 1.06; 95% CI 1.01–1.11; P=0.031) were independent predictors of increased all-cause mortality. Kaplan-Meier Survival Curve Conclusion Among heart failure patients with preserved ejection fraction and moderate-to-severe or severe SMR, surgical or trans-catheter mitral-valve repair or replacement resulted in lower all-cause mortality compared to conservative treatment after 9 years of follow-up.