Diabetes represents a serious health problem. In the diabetic state, alterations in metabolism, increased susceptibility to infections and immunological changes occur. The suppression of the immune response has been identified as a relevant factor that contributes to the increase in the rate of infections in these patients. At the same time, breast cancer is the most frequent malignant tumor in women. The molecular and cellular mechanisms underlying cancer development have revealed that immune cells functionally regulate epithelial cancer development and progression. Breastfeeding has been hypothesized to reduce the risk of breast cancer. However, early systematic reviews have not yielded consistent findings for this association. The demand for human milk is increasing due to the promotion and consumer acceptance of the health benefits of consuming a natural product rich in bioactive components. However, due to changes in glucose metabolism, the components of the milk from diabetic women are modified depending on the time of evaluation. In this literature review, we summarize important new findings revealing the paradoxical role of breastfeeding in preventing the onset of breast cancer in diabetic mothers. We hypothesized that the milk component production in diabetic mothers is affected by changes in glucose metabolism. Therefore, adequate maternal glycemic control and an adequate duration of breastfeeding for diabetic mothers are crucial to ensure that the immunity components are able to confer protection against breast cancer.