The immune properties of breastmilk are the most effective preventative means of reducing infant mortality through both passive and active immunity. Breastmilk for term infants has been linked to decreased incidence of respiratory and ear infections and gastrointestinal distress. This protection is even more important for the preterm infant. Prematurity is one of the leading causes of infant death in the United States. Hospitalized infant outcomes associated with consumption of breastmilk are shorter length of stay and decreased incidence of nosocomial infections and necrotizing enterocolitis (NEC). The presence of nosocomial infections and necrotizing enterocolitis increases risk of preterm mortality and morbidity as well as healthcare expenditures. However, breastmilk immunological components such as secretory immunoglobulin A, lactoferrin (LFT), and cytokines provide a framework of immunity that, in conjunction with nutritional support, significantly improves neonatal health. The relationship between maternal characteristics and breastmilk immune properties is central to further the understanding of the impact of breastmilk on preterm infant morbidity and mortality. The purpose of this article is to review the numerous immune components in breastmilk, the moderators of the immune components, and the relevance of these components to preterm/infant health. Exploration of the complexity of breastmilk immune components may direct future development of interventions to improve and sustain the immunological benefits of preterm breastmilk.