A wide range of breast lesions can arise during pregnancy and lactation, from benign or inflammatory diseases to malignant tumors. Hormone-influenced physiological changes of the breast make the radiological evaluation of breast lesions challenging. Knowledge of the imaging features of normal physiological changes and common breast lesions during this period can help radiologists accurately diagnose and appropriately manage conditions. As such, this pictorial essay illustrates normal physiological changes related to pregnancy and lactation, as well as common benign and malignant breast lesions encountered during those periods.