Iron deficiency is the world’s most common nutrient deficiency according to the World Health Organization. Iron deficiency is especially prevalent in undeveloped countries and rural areas. A double-blind, cluster-randomized design was used among 359 10-17 year old Bangladeshi girls in a three arm trial. Iron-fortified lentils, non-fortified lentils, and no lentil (usual intake) were served to the girls over 4 months with a 100% compliance rate. Blood biomarkers and cognition were assessed using ANCOVAs with group as a factor and age as a covariate. Participants in the fortified lentil condition showed better blood iron status at endline (Hb, sFt, sFtR, TBI) than the other groups. The fortified lentil group also performed better on cognitive measures. Implementing iron-fortified lentils into rural areas may be an effective way to protect against cognitive deficits associated with iron deficiency. Keywords: iron deficiency, anemia, cognition, biomarkers, Bangladesh, adolescent