Postconcussive symptoms after mild traumatic brain injury (MTBI) may be exacerbated by anxiety associated with posttraumatic stress. The aim of this study was to investigate the relationship between postconcussive symptoms and posttraumatic stress disorder (PTSD) in an MTBI population. Survivors of motor vehicle accidents who either sustained an MTBI (N = 46) or no TBI (N = 59) were assessed 6 months posttrauma for PTSD and postconcussive symptoms. Postconcussive symptoms were more evident in MTBI patients with PTSD than those without PTSD, and in MTBI patients than non-TBI patients. Further, postconcussive symptoms were significantly correlated with PTSD symptoms. These findings indicate that postconcussive symptoms may be mediated by an interaction of neurological and psychological factors after MTBI.