Justice-involved veterans are a special population with unique mental health needs compared with other veterans or justice-involved adults. Prevalence estimates of mental health concerns of justice-involved veterans across 18 samples of these veterans (1987-2013), including both incarcerated and community samples, were identified through a systematic literature search of published studies supplemented by Department of Veterans Affairs Veterans Justice Programs data. Despite heterogeneity across samples and measures used, the review highlights several prominent mental health concerns among veterans. Many justice-involved veterans have likely experienced at least one traumatic event, and many have post-traumatic stress disorder (prevalence from 4% to 39% across samples). At least half of justice-involved veterans have an alcohol and/or drug use disorder (estimates as high as 71% and 65%, respectively), and other psychiatric disorders, such as depression (14%-51%) and psychotic disorders (4%-14%), are common. Justice-involved veterans with comorbid substance use and psychiatric disorders are at increased risk of negative outcomes, including homelessness and violent behavior. Overall, comparisons of justice-involved veterans with other justice-involved adults found a slightly higher rate of mental health concerns among justice-involved veterans, with some indication that intravenous drug use is more prevalent. Compared with other veterans, justice-involved veterans have consistently higher rates of mental health concerns, particularly substance use disorders.