Because of workforce needs and demographic and chronic disease trends, nurse practitioners (NPs) and physician assistants (PAs) are taking a larger role in the primary care of medically complex patients with chronic conditions. Research shows good quality outcomes, but concerns persist that NPs' and PAs' care of vulnerable populations could increase care costs compared to the traditional physician-dominated system. We used 2012-13 Veterans Affairs data on a cohort of medically complex patients with diabetes to compare health services use and costs depending on whether the primary care provider was a physician, NP, or PA. Case-mix-adjusted total care costs were 6-7 percent lower for NP and PA patients than for physician patients, driven by more use of emergency and inpatient services by the latter. We found that use of NPs and PAs as primary care providers for complex patients with diabetes was associated with less use of acute care services and lower total costs.