Patients with heart failure with preserved ejection fraction (HFpEF) frequently develop atrial fibrillation (AF). There are no randomized trials examining the effects of AF ablation on HFpEF outcomes.The aim of this study is to compare the effects of AF ablation vs usual medical therapy on markers of HFpEF severity, including exercise hemodynamics, natriuretic peptide levels, and patient symptoms.Patients with concomitant AF and HFpEF underwent exercise right heart catheterization and cardiopulmonary exercise testing. HFpEF was confirmed with pulmonary capillary wedge pressure (PCWP) of 15 mm Hg at rest or ≥25 mm Hg on exercise. Patients were randomized to AF ablation vs medical therapy, with investigations repeated at 6 months. The primary outcome was change in peak exercise PCWP on follow-up.A total of 31 patients (mean age: 66.1 years; 51.6% females, 80.6% persistent AF) were randomized to AF ablation (n = 16) vs medical therapy (n = 15). Baseline characteristics were comparable across both groups. At 6 months, ablation reduced the primary outcome of peak PCWP from baseline (30.4 ± 4.2 to 25.4 ± 4.5 mm Hg; P < 0.01). Improvements were also seen in peak relative VO (20.2 ± 5.9 to 23.1 ± 7.2 mL/kg per minute; P < 0.01), N-terminal pro brain natriuretic peptide levels (794 ± 698 to 141 ± 60 ng/L; P = 0.04), and MLHF (Minnesota Living with Heart Failure) score (51 ± -21.9 to 16.6 ± 17.5; P < 0.01). No differences were detected in the medical arm. Following ablation, 50% no longer met exercise right heart catheterization-based criteria for HFpEF vs 7% in the medical arm (P = 0.02).2AF ablation improves invasive exercise hemodynamic parameters, exercise capacity, and quality of life in patients with concomitant AF and HFpEF.