To evaluate the effect of iron intervention on physical growth in fetuses, infants, children, and adolescents up to 18 years of age, a systematic review with meta-analysis of randomized controlled trials (RCTs) was conducted. Structured electronic searches were conducted to February 2010 using MEDLINE, Embase, and the Cochrane Library databases. RCTs that included iron-fortified foods, iron-fortified formula, or iron supplements and in which height, weight, mid-arm circumference (MAC), head circumference, birth weight, or length of gestation was evaluated were analyzed for inclusion. In total, 21 RCTs in infants, children, and adolescents and 7 studies in pregnant women met the inclusion criteria. The overall pooled result (random-effects model) showed no significant effects of iron intervention on any of the parameters measured. To accommodate wide heterogeneity, studies were stratified according to dose of iron, duration of intervention, age, and baseline iron status. However, only doses of 40–66 mg of supplemental iron and intervention in children ≥6 years of age showed a slight but significant association with weight and MAC.