Human milk is the best food for human infants, including those born preterm. Human milk feeding benefits the preterm infant by improving mental and motor development, decreasing the risk of necrotizing enterocolitis, sepsis, and retinopathy of prematurity during the postnatal period spent in the Neonatal Intensive Care Unit. In order to support the increased nutrient requirements of these infants, human milk must be fortified. In the absence of a mother's own milk, donor human milk is becoming a more commonly used replacement for bovine-based formula, especially in the tiniest patients. While donor human milk has been shown to convey many of the benefits of mother's own milk, it is generally lower in protein and calories than preterm milk and may require fortification in different proportions. This report discusses the evidence for donor human milk in the nutritional support of the preterm infant.