Objective The World Health Organization Collaborating Centre Task Force on Mild Traumatic Brain Injury (MTBI) published its findings on the prognosis of MTBI in 2004. This is an update of that review with a focus on deployed military personnel. Data Sources Relevant literature published between January 2001 and February 2012 listed in MEDLINE and 4 other databases. Study Selection Controlled trials and cohort and case-control studies were selected according to predefined criteria. After 77,914 titles and abstracts were screened, 13 articles were rated eligible for this review and 3 (23%) with a low risk of bias were accepted. Two independent reviewers critically appraised eligible studies using a modification of the Scottish Intercollegiate Guidelines Network criteria. Data Extraction The reviewers independently extracted data from eligible studies and produced evidence tables. Data Synthesis The evidence was synthesized qualitatively and presented in evidence tables. Our findings are based on 3 studies of U.S. military personnel who were deployed in Iraq or Afghanistan. We found that military personnel with MTBI report posttraumatic stress disorder and postconcussive symptoms. In addition, reporting of postconcussive symptoms differed on the basis of levels of combat stress the individuals experienced. The evidence suggests a slight decline in neurocognitive function after MTBI, but this decline was in the normal range of brain functioning. Conclusions We found limited evidence that combat stress, posttraumatic stress disorder, and postconcussive symptoms affect recovery and prognosis of MTBI in military personnel. Additional high-quality research is needed to fully assess the prognosis of MTBI in military personnel.