Background Post-traumatic headache (PTH) occurs in up to 82% of patients with traumatic brain injury (TBI). Post-traumatic stress disorder (PTSD) occurs in 39% of those with TBI. This study evaluates whether PTSD affects PTH disability. Methods 151 consecutive patients with TBI were evaluated from a secondary care trauma centre. Headache disability was assessed using the Headache Impact Test version 6 (HIT 6) and PTSD using PTSD Check List Civilian version (PCL-C). Results In patients with chronic PTH, increased PTSD symptoms were significantly associated with increased headache disability (p<0.001), as were employment status and loss of consciousness (p=0.049 and 0.016, respectively). Age was negatively correlated with headache disability (Spearman's correlation −0.361, p=0.001). Conclusion Increased PTSD severity is significantly associated with increased headache disability in patients with chronic PTH. Managing PTSD in patients with chronic PTH may facilitate headache management.