BACKGROUND: People experiencing homelessness face profound sexual health inequities, driven by overlapping structural vulnerabilities including housing instability, stigma, limited healthcare access, and social exclusion, as well as the complex lived realities associated with homelessness. Interventions designed to improve sexual health outcomes within this population are diverse, ranging from peer-led education to nurse-led clinical models and structural supports such as housing. However, the effectiveness of these interventions depends not only on their content but also on the contexts in which they are delivered and the circumstances of the populations they serve. A realist review seeks to understand how and why interventions work, for whom, and under what conditions by identifying context-mechanism-outcome configurations (CMOCs) that explain how outcomes are generated.

METHODS: This review will follow Pawson's six-step realist synthesis methodology. An initial programme theory has been developed through preliminary literature searches and will be refined iteratively as new evidence is gathered. Published and grey literature will be systematically searched and selected for their relevance to developing and testing CMOCs. Data extraction will focus on identifying key information which can contribute to understanding contextual factors, mechanisms, and outcomes across intervention types. The synthesis will develop, refine, and test theories that explain how sexual health interventions produce change in varied contexts. Patient and public involvement contributors will be consulted throughout the review to validate findings and support interpretation.

CONCLUSION: This review will generate transferable insights into how sexual health interventions for people experiencing homelessness work across different contexts. By identifying mechanisms that generate outcomes, and the conditions that shape them, the findings will support more context-sensitive and effective policy, practice, and service design. The results will be disseminated through peer-reviewed publications, practitioner-facing summaries, and community-informed outputs.