Current treatment recommendations for patients with heart failure and secondary mitral regurgitation include transcatheter edge-to-edge repair and mitral-valve surgery. Data from randomized trials comparing these therapies are lacking in this patient population. In this noninferiority trial conducted in Germany, patients with heart failure and secondary mitral regurgitation who continued to have symptoms despite guideline-directed medical therapy were randomly assigned, in a 1:1 ratio, to undergo either transcatheter edge-to-edge repair (intervention group) or surgical mitral-valve repair or replacement (surgery group). The primary efficacy end point was a composite of death, hospitalization for heart failure, mitral-valve reintervention, implantation of an assist device, or stroke within 1 year after the procedure. The primary safety end point was a composite of major adverse events within 30 days after the procedure. A total of 210 patients underwent randomization. The mean (±SD) age of the patients was 70.5±7.9 years, 39.9% were women, and the mean left ventricular ejection fraction was 43.0±11.7%. Within 1 year, at least one of the components of the primary efficacy end point occurred in 16 of the 96 patients with available data (16.7%) in the intervention group and in 20 of the 89 with available data (22.5%) in the surgery group (estimated mean difference, -6 percentage points; 95% confidence interval [CI], -17 to 6; P<0.001 for noninferiority). A primary safety end-point event occurred in 15 of the 101 patients with available data (14.9%) in the intervention group and in 51 of the 93 patients with available data (54.8%) in the surgery group (estimated mean difference, -40 percentage points; 95% CI, -51 to -27; P<0.001). Among patients with heart failure and secondary mitral regurgitation, transcatheter edge-to-edge repair was noninferior to mitral-valve surgery with respect to a composite of death, rehospitalization for heart failure, stroke, reintervention, or implantation of an assist device in the left ventricle at 1 year. (Funded by Abbott Vascular; MATTERHORN ClinicalTrials.gov number, NCT02371512.).