It has been unequivocally proven that human breast milk is the ideal source of nutrition for infants. However, mothers of preterm infants face a number of barriers to providing sufficient milk volume to their babies, who are at risk for developing necrotizing enterocolitis (NEC). Donated milk, distributed through milk banks, is becoming a desirable alternative to formula feeding, and is increasingly being considered for hospitalized, preterm infants in North America. Donor milk in North America is pasteurized (62.5 °C, 30 min) to remove possible infectious contaminants; a number of immune and bioactive components are either partially or entirely inactivated by this process. Identifying the impact of pasteurization on immune components of breast milk has been the focus of numerous research studies over the past several decades. The objective of this review is to summarize the literature on the feeding of pasteurized donor milk to preterm infants and the current understanding of the impact of pasteurization on immune components of breast milk, with particular reference to those implicated in the prevention of NEC.