This study examined the role of autonomy support from adults’ informal health supporters (family or friends) in diabetes-specific health behaviors and health outcomes. Using baseline data from 239 Veterans with type 2 diabetes at risk of complications enrolled in behavioral trial, we examined associations between autonomy support from a support person and that support person’s co-residence with the participant’s diabetes self-care activities, patient activation, cardiometabolic measures, and predicted risk of a cardiac event. Autonomy support from supporters was associated with significantly increased adherence to healthy lifestyle behaviors (diet, p < .001 and exercise, p = .003); higher patient activation (p < .001); greater patient efficacy in interacting with healthcare providers, and lower 5-year (p = .044) and 10-year (p = .027) predicted cardiac risk. Autonomy support was not significantly associated with diabetes-specific behaviors (checking blood glucose, foot care, or medication taking); or hemoglobin A1c, systolic blood pressure, or non-HDL cholesterol. There was a significant interaction of autonomy support and supporter residence in one model such that lack of autonomy support was associated with lower patient activation only among individuals with in-home supporters. No other interactions were significant. Findings suggest that autonomy support from family and friends may play a role in patient self-management, patient activation, and lower cardiac risk.