Abstract: Introduction: Headache is the most overwhelmingly reported symptom following mild traumatic brain injury (mTBI). The upper cervical spine has been implicated in headache etiology, and cervical dysfunction may result in neck pain that influences the experience of headache. Sleep problem is the second most reported symptom following mTBI. We explored the contribution of neck pain (as a potential proxy for cervical dysfunction) on headache burden along with the contribution of sleep quantity following mTBI. Materials and Methods:Retrospective data from a repository consisting of service members recruited from primary care, with (N = 493) and without a history of mTBI (N = 63), was used for analysis. Portions of the Neurobehavioral Symptom Inventory, Pittsburgh Sleep Quality Index, and Orebro Musculoskeletal Pain Questionnaire were used for headache, sleep, and neck pain measures. Results: Demographic and military characteristics that differed between groups were treated as covariates in analyses. Group comparisons revealed significant differences in the expected direction on all measures: mTBI > controls on headache and neck pain; controls > mTBI on sleep quantity. Regression revealed that neck pain accounted for the most variance in headache score, followed by group membership and sleep quantity. When analyzing groups separately, no difference in the pattern of results was revealed in the mTBI group. In the control group, variance in headache score was only significantly related to neck pain. Conclusions: Amongst service members who sought service from primary care, neck pain explains more variance in headache burden than mTBI history or sleep quantity, supporting that cervical dysfunction may be a salient factor associated with headache. Neck functioning may be a potential area of intervention in the management of headaches.