A comprehensive understanding of the social and psychological impact of diabetes mellitus is important for informing policy and practice. One potentially significant, yet under-researched, issue is the social stigma surrounding diabetes. This narrative review draws on literature about health-related stigma in diabetes and other chronic conditions in order to develop a framework for understanding diabetes-related stigma. Our review of the literature found that people who do not have diabetes assume that diabetes is not a stigmatized condition. In contrast, people with diabetes report that stigma is a significant concern to them, experienced across many life domains, e.g., in the workplace, in relationships. The experience of diabetes-related stigma has a significant negative impact on many aspects of psychological well-being and may also result in sub-optimal clinical outcomes for people with diabetes. We propose a framework that highlights the causes (attitudes of blame, feelings of fear and disgust, and the felt need to enforce social norms and avoid disease), experiences (being judged, rejected, and discriminated against), and consequences (e.g., distress, poorer psychological well-being, and sub-optimal self-care) of diabetes-related stigma and also identifies potential mitigating strategies to reduce diabetes-related stigma and/or enhance coping and resilience amongst people with diabetes. The systematic investigation of the experiences, causes, and consequences of diabetes-related stigma is an urgent research priority.