In most mammals, milk is the only food source for newborns, and, consequently, it must contain all the key nutrients for normal growth and development. Environmental factors and the diet of the mother can affect the composition of the milk. In this chapter, we describe how perinatal and direct exposure to bisphenol A (BPA) disrupts the functional differentiation of the mammary gland and alters milk synthesis, composition and production. Milk protein and lipid synthesis are affected by exposure to BPA through different hormonal signaling pathways, cell–extracellular matrix interactions, epigenetic alterations, and the classical estrogenic pathway. These changes in the composition of the produced milk may compromise the growth and development of the offspring.