Persistent post-concussive symptoms (PPCS) are debilitating symptoms that endure beyond the usual recovery period after concussion. Post-traumatic headache is one of the most common symptoms of concussion and its pathophysiology remains poorly characterized. Oxidative stress may contribute to the symptoms seen in PPCS patients. Here, we use edited magnetic resonance spectroscopy to investigate levels of the antioxidant glutathione in the anterior cingulate and sensorimotor cortices in adults with PPCS relative to controls. In the anterior cingulate—a critical hub in the default mode network—we found a significant positive correlation between glutathione and functional impact of headache in PPCS patients.