Diabetes self-care is a critical aspect of disease management for adults with diabetes. Since family members can play a vital role in a patient’s disease management, involving them in self-care interventions may positively influence patients’ diabetes outcomes. We systematically reviewed family-based interventions for adults with diabetes published from 1994 to 2014 and assessed their impact on patients’ diabetes outcomes and the extent of family involvement. We found 26 studies describing family-based diabetes interventions for adults. Interventions were conducted across a range of patient populations and settings. The degree of family involvement varied across studies. We found evidence for improvement in patients’ self-efficacy, perceived social support, diabetes knowledge, and diabetes self-care across the studies. Owing to the heterogeneity of the study designs, types of interventions, reporting of outcomes, and family involvement, it is difficult to determine how family participation in diabetes interventions may affect patients’ clinical outcomes. Future studies should clearly describe the role of family in the intervention, assess quality and extent of family participation, and compare patient outcomes with and without family involvement.