Atrial fibrillation (AF) is the most prevalent cardiac arrhythmia and it increases the risk of thromboembolic stroke and death. AF is common in patients with heart failure and reduced ejection fraction (HFrEF), affecting between 30 and 40% of patients with HFrEF. AF increases the risk of death and hospitalization in patients with HFrEF. Only two antiarrhythmic drugs (amiodarone and dofetilide) are guideline-recommended in patients with AF and heart failure (HF). Meta-analyses of studies of major trials in HF suggest that patients with AF/HFrEF do not benefit from conventional β-blockers. Bucindolol has shown promise in the treatment of patients with AF/HFrEF. We will explore how the shared pathophysiology of AF/HF is targeted by the unique pharmacology of bucindolol and review the existing data for bucindolol in AF/HF. We will explore findings that support a pharmacogenetically modulated effect of bucindolol in patients with polymorphisms in β1-adrenergic receptor and provide an overview of ongoing studies.