Iron deficiency is the most common nutrient deficiency in the world. Epidemiological data indi- cate that iron deficiency is more prevalent in infants, in preschool-children, and in adolescents. Etiologies of iron deficiency in children include inadequate dietary iron intake, which is the most common cause, as well as increased iron requirements, bleeding, and intestinal iron absorption disorders. Iron deficiency can lead to symptoms related to anemia, may interfere with neuro- development and may cause skin, hair, nail, and gastrointestinal problems. This review focuses on the causes, signs, symptoms, diagnosis and management of iron deficiency in infancy, child- hood, and adolescence.