Background: Working in humanitarian crisis situations is dangerous. National humanitarian staff in particular face the risk of primary and secondary trauma exposure which can lead to mental health problems. Despite this, research on the mental health of national staff is scarce, and a systematic analysis of up-to-date findings has not been undertaken yet. Objective: This article reviews the available literature on trauma-related mental health problems among national humanitarian staff. It focuses on the prevalence of selected mental health problems in relation to reference groups; sex and/or gender as predictive factors of mental health problems; and the influence of organization types on mental health problems. Method: Three databases were systematically searched for relevant studies published in the English language in peer-reviewed journals. Results: Fourteen articles matched the inclusion criteria. Findings suggest that national staff experience mental health problems and the prevalence of posttraumatic stress disorder, depression, and anxiety among this occupation group is mostly similar to or higher than among reference groups. Research on both substance use disorder and suicidal behavior among national staff is particularly scarce. The relation between sex and/or gender and mental health problems among national staff appears to be complex, and organizational staff support seems to be an important determinant for mental health. Conclusion: All findings call for increased attention from the humanitarian community and further research on the topic.