As diabetes becomes more prevalent in younger women, diabetes and maternal-child health issues such as breastfeeding co-exist with increasing frequency. We sought to determine the relationship between breastfeeding and both type 2 diabetes and gestational diabetes (GDM) in a variety of clinical contexts, with a focus on prevention. The Medline database from 1966-2003, relevant references of selected articles, the Cochrane database, and the NIH Clinical Trials website were searched. Search terms included breastfeeding, infant nutrition, and diabetes. The search was restricted to the English language and human subjects. Each study was reviewed by at least two of the authors and included if it pertained to the relationship between type 2 diabetes or GDM and breastfeeding. Twelve of 15 identified studies (80%) met selection criteria. All studies were observational. Specific maternal-child health populations varied by study. Two of the authors abstracted information from each article on 1) study design, 2) target population, 3) sample size/power, 4) definition of breastfeeding, 5) definition of diabetes, and 6) confounders. Higher rates of pregnancy and neonatal complications among women with type 2 or gestational diabetes can pose significant challenges to breastfeeding. Low estrogen levels in breastfeeding women may have a protective effect on glucose metabolism and subsequent risk of diabetes. Having been breastfed for at least 2 months may lower the risk of diabetes in children. Initial research has begun on the long-term effects of diabetes during pregnancy on children. Breastfeeding may lower both maternal and pediatric rates of diabetes. Women with diabetes should be strongly encouraged to breastfeed because of maternal and childhood benefits specific to diabetes that are above and beyond other known benefits of breastfeeding.