Atrial fibrillation (AF) and heart failure (HF) are evolving epidemies, together responsible for substantial human suffering and health-care expenditure. The simultaneous co-hexistence of the two conditions is associated with mortality rates higher than those observed in individuals with only one or none of them. Patients with concomitant HF and AF suffer from even worse symptoms and poorer prognosis, yet evidence-based evaluation and management of this group of patients is lacking. In this review, we evaluate the common mechanisms for the development of AF in HF patients and vice versa, focusing on the evidence for potential treatment strategies. Recent data have suggested that these patients may respond differently if compared to those with HF or AF alone. These results highlight the clear clinical need to identify and treat these diseases according to best evidence, in order to prevent adverse outcomes and reduce the huge burden that HF and AF are expected to have on global healthcare systems in the future.