Objective: Females in the military report greater post-concussive symptoms than males following a mild traumatic brain injury (mTBI) (Iverson, et al. 2011; Brickell et al 2014). This study explored the impact gender has on outcome following mTBI with focus on the interaction between post-concussive symptoms and post-traumatic stress (PTS). Method: 86 female service members with a history of concussion were included in the study as well as 86 matched male service members based on nine variables: TBI severity, injury mechanism, bodily injury, days post injury, age, deployment history, theater where wounded, military branch, and rank. Concussion was based on comprehensive evaluation of medical records and self-report history. Post-concussive symptoms were from the Neurobehavioral Symptom Inventory (NSI). PTS was classified as either “absent” or “present” based on moderate or higher self-reported symptoms of hyper-vigilance, avoidance, and re-experiencing on the Post-traumatic Stress Disorder-Checklist Civilian.Results: 30.2% of the males and 39.5% of the females had positive PTS based on symptom severity. An ANOVA revealed a significant interaction between PTS symptom severity and Gender, F (1, 168) = 5.24, p = 0.023. When PTS met criteria, genders did not differ in terms of severity of post-concussive symptoms (t = 0.25, p = 0.806, d =0.07). In contrast, when PTS was absent (i.e., did not meet criteria), there was a moderate difference between the genders (t = −3.60, p = 0.001, d = 0.68). Conclusion: Females tend to have poorer outcome than males following mTBI (i.e., increased self-reported post-concussive symptoms) only when there are low levels of PTS symptoms. When PTS are high, there are no differences in post-concussion symptoms between males and females. This finding is limited by the self-reported nature of symptoms opposed to clinician confirmed diagnosis of PTS. The views expressed herein are those of the authors and do not necessarily reflect the official policy or position of the Department of the Navy, Department of Defense, or the United States government.