Adults with type 2 diabetes mellitus (T2DM) often receive self-management support from adult children, siblings or close friends residing outside of their home. However, the role of out-of-home support in patients’ self-management and well-being is unclear. Patients (N = 313) with HbA1c > 7.5% were recruited from community primary care clinics for a mobile health intervention trial and identified an out-of-home informal support person, herein called a CarePartner: 38% also had an in-home supporter.