The present review outlines the role of breastfeeding in diabetes. In the mother, breastfeeding has been suggested to reduce the incidence of type 2 diabetes mellitus, the metabolic syndrome and cardiovascular disease. Moreover, it appears to reduce the risk of premenopausal breast cancer and ovarian cancer. In the neonate and infant, among other benefits, lactation confers protection from future both type 1 and type 2 diabetes. Whether lactation protects women with gestational diabetes mellitus and their offspring from future T2DM remains to be answered. Importantly, for diabetic mothers, antidiabetic treatment itself may affect breastfeeding. There is not enough data to allow the use of oral hypoglycaemic agents. Therefore, insulin currently remains the optimal antidiabetic treatment during lactation. In conclusion, breastfeeding could be considered a modifiable risk factor for the development of diabetes and even a potential protective lifestyle measure from future cardio-metabolic and malignant diseases. Therefore, health care professionals should encourage both women with and without diabetes to breastfeed their children.