Diabetes is a very important and preventable risk factor for the development of heart failure and a frequent comorbidity observed in patients with heart failure with increased cardiovascular morbidity and mortality. Therefore, it is of clinical importance to treat both diseases as early as possible with an optimal therapy. This joint position paper of the German Cardiac Society (DGK) and German Diabetes Society (DDG) outlines the scientific evidence and provides recommendations about diagnostics and treatment of heart failure and diabetes in order to improve the outcome.