Genomic imprinting is an epigenetically regulated process leading to gene expression according to its parental origin. Imprinting is essential for prenatal growth and development, regulating nutritional resources to offspring, and contributing to a favoured theory about the evolution of imprinting being due to a conflict between maternal and paternal genomes for the control of prenatal resources – the so-called kinship hypothesis. Genomic imprinting has been mainly studied during embryonic and placental development, however, maternal nutrient provisioning is not restricted to the prenatal period. In this context, the mammary gland acts at the maternal-offspring interface providing milk to the newborn. Maternal care including lactation supports the offspring, delivering nutrients and bioactive molecules protecting against infections and contributing to healthy organ development and immune maturation. The normal developmental cycle of the mammary gland – pregnancy, lactation, involution - is vital for this process, raising the question of whether genomic imprinting might also play a role in postnatal nutrient transfer by controlling mammary gland development. Characterising the function and epigenetic regulation of imprinted genes in the mammary gland cycle may therefore provide novel insights into the evolution of imprinting since the offspring’s paternal genome is absent from the mammary gland, in addition to increasing our knowledge of postnatal nutrition and its relation to life-long health.