The aim of this study was to determine the prognostic utility of baseline functional status and its impact on the outcomes of transcatheter mitral valve repair (TMVr) in patients with heart failure (HF) with secondary mitral regurgitation (SMR). The COAPT (Cardiovascular Outcomes Assessment of the MitraClip Percutaneous Therapy for Heart Failure Patients With Functional Mitral Regurgitation) trial demonstrated that TMVr with the MitraClip in patients with HF with moderate to severe or severe SMR improved health-related quality of life. The clinical utility of a baseline assessment of functional status for evaluating prognosis and identifying candidates likely to derive a robust benefit from TMVr has not been previously studied in patients with HF with SMR. The COAPT study was a multicenter, randomized, controlled, parallel-group, open-label trial of TMVr with the MitraClip plus guideline-directed medical therapy (GDMT) versus GDMT alone in patients with HF, left ventricular ejection fraction 20% to 50%, and moderate to severe or severe SMR. Baseline functional status was assessed by 6-min walk distance (6MWD). Patients with 6MWD less than the median (240 m) were older, were more likely to be female, and had more comorbidities. After multivariate modeling, age (p = 0.005), baseline hemoglobin (p = 0.007), and New York Heart Association functional class III/IV symptoms (p < 0.0001) were independent clinical predictors of 6MWD. Patients with 6MWD <240 m versus ≥240 m had a higher unadjusted and adjusted rate of the 2-year composite of all-cause death or HF hospitalization (64.4% vs. 48.6%; adjusted hazard ratio: 1.53; 95% confidence interval: 1.19 to 1.98; p = 0.001). However, there was no interaction between baseline 6MWD and the relative effectiveness of TMVr plus GDMT versus GDMT alone with respect to the composite endpoint (p = 0.633). Baseline assessment of functional capacity by 6MWD was a powerful discriminator of prognosis in patients with HF with SMR. TMVr with the MitraClip provided substantial improvements in clinical outcomes for this population irrespective of baseline functional capacity.