Introduction: Examining costs and utilization in a single-payer universal health care system provides information on fiscal and resource burdens associated with head and neck cancer (HNC). Here, we examine trends in the Department of Defense (DoD) HNC population with respect to: (1) reimbursed annual costs and (2) patterns and predictors of health care utilization in military only, civilian only, and both systems of care (mixed model). Materials and Methods: A retrospective, cross-sectional study was conducted using TRICARE claims data from fiscal years 2007 through 2014 for reimbursement of ambulatory, inpatient, and pharmacy charges. The study was approved by the Defense Health Agency Office of Privacy and Civil Liberties as exempt from institutional review board full review. The population was all beneficiaries, age 18-64, with a primary ICD-9 diagnosis of HNC, on average, 2,944 HNC cases per year. The outcomes of regression models were total reimbursed health care cost, and counts of ambulatory visits, hospitalizations, and bed days. The predictors were fiscal year, demographic variables, hospice use, type and geographic region of TRICARE enrollment, use of military or civilian care or mixed use, cancer treatment modalities, the number of physical and mental health comorbid conditions, and tobacco use. A priori, null hypotheses were assumed. Results: Per annual average, 61% of the HNC population was age 55-64, and 69% were males. About 6% accessed military facilities only for all health care, 60% accessed civilian only, and 34% accessed both military and civilian facilities. Patients who only accessed military care had earlier stage disease as indicated by rates of single modality treatment and hospice use; military care only and mixed use had similar rates of combination treatment and hospice use. The average cost per patient per year was $14,050 for civilian care only, $13,036 for military care only, and $29,338 for mixed use of both systems. The strongest predictors of higher cost were chemotherapy, radiation therapy, head and neck surgery, hospice care, and mixed-use care. The strongest predictors of health care utilization were chemotherapy, use of hospice, the number of physical and mental health comorbidities, radiation therapy, head and neck surgery, and system of care. Conclusions: To a single payer, the use of a single system of care exclusively among HNC patients is more cost-effective than use of a mixed-use system. The results suggest an over-utilization of ambulatory care services when both military and civilian care are accessed. Further investigation is needed to assess coordination between systems of care and improved efficiencies with respect to the cost and apparent over-utilization of health care services.