Abstract: Modern military conflicts including Operation Enduring Freedom/Operation Iraqi Freedom have been associated with increased risk of adverse emotional and cognitive outcomes. Increasingly frequent presentations of posttraumatic stress disorder (PTSD) symptomology and history of non-acute mild traumatic brain injury (mTBI) have been observed in modern cohorts of veterans. Longitudinal associations involving PTSD, mTBI, and neurocognitive symptoms are poorly understood, specifically with regard to long-term PTSD symptom improvement. Thus, the main objective of this study was to evaluate if cognitive performance and history of mTBI could predict PTSD symptom change. The study examined the neuropsychological performance and PTSD symptoms of 47 combat veterans with and without mTBI across multiple cognitive domains at baseline and evaluated PTSD symptoms again after one year. All assessments included the Clinician Administered PTSD Scale (CAPS-IV), a self-administered mTBI screener, and individually administered performance based neurocognitive tests. Analyses revealed that cognition was not a significant predictor of PTSD symptom change; however, mTBI history was related to subsequent PTSD severity when controlling for visual attention performance and age. Screened mTBI was also associated with greater reported PTSD symptoms at both time points and poorer visual memory performance. These results suggest a longitudinal relationship among PTSD and mTBI may contribute to sustained emotional symptoms over time; however, cognitive performance is not a predictor of longitudinal symptom change.