Heart failure (HF) is highly prevalent and associated with adverse outcomes and high costs. Compared with the general population, depression is up to five times more common in HF patients. Comorbid depression increases morbidity and mortality risk and health-care expenditures even further and decreases quality of life. Possible, often interrelated, mediators of these effects include biological, behavioral, and psychosocial factors. Screening instruments such as the self-administered PHQ-2 facilitate detection of patients at risk. Although antidepressants may improve psychological well-being, no positive effects on hard clinical endpoints have been demonstrated to date.