Chronic heart failure (HF) and diabetes mellitus (DM) commonly coexist. Each condition increases the likelihood of developing the other, and when they occur together in the same patient the risk of morbidity and mortality increases markedly. We discuss the epidemiological overlap and consider the complex patho-physiological pathways linking the two diseases. The treatment of each condition is made more problematic by the presence of the other. We review the evidence-based treatment strategies and discuss the common problems faced by physicians when treating patients with both conditions. This article forms a comprehensive overview of a fascinating intersection between two common diseases.