A systematic review was conducted to summarize the evidence currently available from randomized controlled trials (RCTs) concerning the effect of iron intake of infants, children and adolescents on measures of cognitive development and function. The Cochrane Library, MEDLINE and Embase were searched up to and including February 2010. Studies were also identified by checking the bibliographies of the articles retrieved. All RCTs with an adequate control group in which iron supply was provided by natural food sources, fortified foods, formula or supplements to infants, children or adolescents until the age of 18 years were considered for inclusion. No language restrictions were applied. Fourteen studies met the selection criteria. Twelve out of these 14 studies had a high or moderate risk of bias. A large degree of heterogeneity of study populations, iron dosages and outcome measures precluded performing a quantitative meta-analysis. Overall, the studies suggest a modest positive effect of iron supplementation on cognition and psychomotor outcomes in anemic infants and children after supplementation periods of at least 2 months of duration.