Introduction: Iron depleted deposits are the first link in the chain of events leading to iron deficiency which is the most prevalent nutritional shortage and main cause of anemia worldwide. This situation can be prevented through food fortification.Objective: To compare the efficacy of amino acid chelate iron with ferrous sulfate as fortifier of a dietaryc omplement in preschoolers with iron deficiency.Materials and methods: This study was a blinded clinical trial with randomized groups. We analyzed 56 preschoolers with iron deficiency (ferritin < 24 ng/ml) that received 13 g of milk with 12.5 mg of iron, either amino acid chelate or in the ferrous sulfate form. After two months, hemoglobin, hematocrit and serum ferritin concentrations were measured.Results: In the ferrous sulfate group, ferritin concentration increased from 18.8 ng/ml to 24.1 ng/ml,while the variation was of 18.4 ng/ml to 29.7 ng/ml in the amino acid chelate group, with statistically differences in both cases. Serum ferritin was different between groups, being higher in iron aminoacid chelate group (p=0.022). Hemoglobin and hematocrit levels did not change after the intervention. Adverse reactions in the ferrous sulfate group were 35.7%, compared with 42.9% in the iron amino acidc helate group; 5 children had respiratory tract infection, without statistical differences.Conclusions: Both compounds increased serum ferritin concentration, with a higher increase in thosewho were given milk with iron amino acid chelate. There were no differences in the adverse reactionsand infections incidences between the groups. doi: http://dx.doi.org/10.7705/biomedica.v33i3.775