Type 2 diabetes mellitus and congestive heart failure are highly prevalent diseases with significant morbidity and mortality. These 2 diseases often occur concurrently because of shared risk factors such as coronary artery disease, and also because type 2 diabetes mellitus has direct cardiotoxic effects. Type 2 diabetes mellitus likely has a causative role in the development and prognosis of patients with heart failure. Optimal prevention and treatment of type 2 diabetes mellitus and heart failure likely involves identifying and treating their shared pathophysiologic features. Novel drug therapies, such as sodium-glucose co-transporter 2 inhibitors, offer an exciting potential to better understand the relationship between type 2 diabetes mellitus and heart failure, and may prove to have beneficial effects on cardiovascular outcomes in patients affected by these diseases.