Iron deficiency (ID) constitutes an important comorbidity affecting symptoms and outcomes in patients with heart failure (HF). Recent experimental studies and randomized clinical trials have demonstrated important novel data regarding either the mechanisms of this comorbid condition or the beneficial effects of intravenous iron therapy in patients with HF. In this review we summarize new developments regarding ID in patients with HF with either reduced or preserved ejection fraction, along with brief description of ongoing morbidity and mortality trials in this field-4 years after the release of the 2016 European Society of Cardiology guidelines that clearly recommend to screen for, and consider treatment of, ID in patients with HF with reduced ejection fraction.