This study evaluated whether posttraumatic stress disorder (PTSD) mediated the relationship between mild traumatic brain injury (MTBI) and general health ratings, psychosocial functioning, and perceived barriers to receiving mental healthcare 2 years following return from deployment in veterans of Operations Enduring Freedom and Iraqi Freedom (OEF/OIF). A total of 277 OEF/OIF veterans completed the Connecticut OEF/OIF Veterans Needs Assessment Survey; 18.8% of the sample screened positive for MTBI. Compared with respondents who screened negative for MTBI, respondents who screened positive for MTBI were younger, more likely to have PTSD, more likely to report fair/poor overall health and unmet medical and psychological needs, and scored higher on measures of psychosocial difficulties and perceived barriers to mental healthcare. Injuries involving loss of consciousness were associated with greater work-related difficulties and unmet psychological needs. PTSD mediated the relationship between MTBI and all of these outcomes. These results underscore the importance of assessing PTSD in OEF/OIF veterans who screen positive for MTBI.