Anemia associated with heart failure is a frequent condition, which may lead to heart function deterioration by the activation of neuro-hormonal mechanisms. Therefore, a vicious circle is present in the relationship of heart failure and anemia. The consequence is reflected upon the patients' survival, quality of life, and hospital readmissions. Anemia and iron deficiency should be correctly diagnosed and treated in patients with heart failure. The etiology is multifactorial but certainly not fully understood. There is data suggesting that the following factors can cause anemia alone or in combination: iron deficiency, inflammation, erythropoietin levels, prescribed medication, hemodilution, and medullar dysfunction. There is data suggesting the association among iron deficiency, inflammation, erythropoietin levels, prescribed medication, hemodilution, and medullar dysfunction. The main pathophysiologic mechanisms, with the strongest evidence-based medicine data, are iron deficiency and inflammation. In clinical practice, the etiology of anemia needs thorough evaluation for determining the best possible therapeutic course. In this context, we must correctly treat the patients' diseases; according with the current guidelines we have now only one intravenous iron drug. This paper is focused on data about anemia in heart failure, from prevalence to optimal treatment, controversies, and challenges.