Patients with heart failure (HF) frequently experience iron deficiency, with an estimated prevalence of sideropenia around 50%. In HF patients, iron deficiency is associated with reduced functional capacity, lower quality of life, and an increased risk of hospitalizations and mortality. Therefore, timely diagnosis and treatment of sideropenia are essential to improve clinical outcomes in HF patients with reduced or mildly reduced ejection fraction, while data on the benefits of iron supplementation in HF patients with preserved ejection fraction remain limited. This review aims to provide an overview of the prevalence, diagnostic criteria, available evidence, indications, iron formulations, and recommended protocols for identifying and treating iron deficiency in HF patients.