Childhood undernutrition contributes to up to 45% of deaths in children under age 5. Moringa oleifera (moringa) leaves are nutrient dense and promote breastmilk production. We performed a systematic review assessing the impact of moringa leaf supplementation in humans and animals on the outcomes of iron, vitamin A status, the measures of growth, and/or breastmilk production. Our inclusion/exclusion criteria were as follows; inclusion: quantitative primary data assessing the effect of moringa leaf supplementation on humans or animals including any of the outcomes defined earlier with no exclusion for geography, age, or language. Exclusion: full text not available. Our search yielded 148 unique studies; among them, 33 were included (seven human studies and 26 animal studies). Quality assessment by Effective Public Health Practice Project guidelines was strong for one study and moderate for all other studies. In humans, moringa at higher (14-30 g/day) not lower (<10 g/day) doses improved hemoglobin (Hgb) in children with iron deficiency anemia, improved Hgb and vitamin A status in postmenopausal women, and increased BMI in HIV+ underweight adults. Moringa (0.5 g/day) also increased breastmilk volumes. In animals, moringa increased milk production in two of three studies, inconsistently affected growth, and had no effect on iron status. Evidence on moringa supplementation's utility is limited but promising. Larger, more rigorous trials are needed to characterize its impact.