Background: Modern slavery is a term which incorporates a range of exploitative situations that involve the violation of human rights and the subjugation of individuals. It presents a significant public health concern. Post-release, survivors of modern slavery have complex mental health needs. Whilst mental health provision is a component of international and national policy, the delivery of evidence-based support remains a gap in the global anti-slavery response. Aim: To identify and synthesise the evidence base for mental health interventions developed and evaluated for use in a post-slavery survivor population. Methods: A systematic literature review was undertaken. The review protocol was prospectively registered with PROSPERO and followed the PRISMA guidance in its reporting. A multi-stage search strategy was utilised to retrieve studies. Quality appraisal was undertaken using the QualSyst tool. Due to heterogeneity in study design, a narrative approach to synthesising the findings was undertaken. Results: Nine studies met the final inclusion criteria. The narrative synthesis clustered the studies in three themes: study design and population; type of intervention; and outcomes reported. The included studies focussed on specific subpopulations, namely child soldiering, child labour or sex trafficking. Conclusion: This review has highlighted not only important theory-practice gaps in relation to the provision of evidence-based mental health support but scant evidence limited to specific sub-groups (child soldiering, child labour or sex trafficking). The emphasis placed on PTSD within the interventions tested risks mental health support becoming exclusionary to those with other needs. When assessing intervention efficacy, the complex socio-political context in which survivors exist as well as the increasing emphasis on holistic care, personal recovery and lived experience need to be considered. Taking this into account, the case can be made for the inclusion of a wider range of non-clinical outcomes in the assessment of mental health intervention effectiveness.