Diabetes mellitus is the subject of a great many case management programs around the world as it is a prevalent disease with modifiable risk factors and potentially preventable severely disabling complications. Diabetes mellitus represents even greater challenges in the context of mental illness. Patients with psychological complications of diabetes mellitus or with psychiatric disease and comorbid diabetes mellitus present a unique set of problems with which the physician and other care providers must contend. These challenges include: problems with treatment regimens; inability to manage self-care programs; difficulties with negotiating appointments, referrals, and follow-up care; confusion over competing care instructions; potential drug interactions and/or complications which exacerbate diabetes mellitus; and many social difficulties which undermine the effective care of diabetes mellitus.Lack of control of either diabetes mellitus or mental health problems may complicate or exacerbate one or the other of these diseases. Case management for these individuals is one potential way of improving care. Management needs to be team based, coordinated between specialties, simplified, and in one location of care when possible. Excellent coordination and communication is paramount and social factors and supports require special attention.