Depression in people with diabetes is linked to poor physical health. Social support and physical health have been linked to each other and to depression. The present study examined three possible models of the interrelationship among depression, social support, and diabetes-related medical symptoms. Eighty-six diabetes patients completed measures of diabetes symptoms, depression, and diabetes-related social support. Depression, social support, and diabetes-related medical symptoms were significantly related to each other. Mediation analysis indicated that the effect of social support on diabetes-related medical symptoms was fully accounted for by social support's adverse effect on depression. Consistent with theory and research on interpersonal aspects of depression, a bi-directional relationship between depression and social support was suggested. That is, while both diabetes-related medical symptoms and social support independently contributed to depression, depression also contributed to lower social support. Findings underscore the potential importance of interpersonal factors in the physical health of individuals with diabetes.