Background: Headache is a significant problem often seen following traumatic brain injury (TBI) in U. S. military veterans. Cervicogenic headache, which originates from the soft tissues and bones of the neck, is a subtype of headache often associated with TBI. Methods: In this case series of military veterans with a history of TBI at a Veterans Affairs Medical Center outpatient clinic, we examined the efficacy of Osteopathic Manipulative Therapy (OMT) in reducing the severity of pain associated with cervicogenic headache as measured on a 0-10 numeric pain rating scale. Secondary outcome measures include the percentage of patients who reported feelings of sadness and anxiousness, measures of neck range of motion pre-treatment and post-treatment, total score on the Pittsburgh Sleep Quality Index and incidence of adverse events. Subjects: Patients included were at least eighteen years of age, had been previously diagnosed with mild traumatic brain injury and cervicogenic headache, had clinical symptoms and radiographic imaging study findings of cervical spine degeneration, had at least two OMT treatments for cervicogenic headaches and completed a follow up evaluation. Results: In eight patients included in the case series, there were consistent reductions in headache pain as determined by a pain scale score after the treatments. There were statistically significant improvements in some measures of neck range of motion and a statistically significant reduction in anxiety after only one treatment. There was not a statistically significant improvement in sad mood or sleep, and one self-limited adverse event was reported. Conclusion: Osteopathic Manipulative Therapy is an effective and safe technique in the treatment of cervicogenic headache in patients with mild traumatic brain injury.