IntroductionHumanitarian migrants often suffer from poor health, including oral health. Reasons for their oral health conditions include difficult migration trajectories, poor nutrition and limited financial resources. Oral health promotion is crucial for improving oral health-related quality of life of humanitarian migrants. While community-level oral health promotion programmes for humanitarian migrants have been implemented (eg, in host countries and refugee camps), there is scant literature evaluating their transferability or effectiveness. Given that these programmes yield unique context-specific outcomes, the purpose of this study is to understand how community-level oral health promotion programmes for humanitarian migrants work, in which contexts and why.Methods and analysisRealist review, a theory-driven literature review methodology, incorporates a causal heuristic called context–mechanism–outcome configurations to explain how programmes work, for whom, and under which conditions. Using Pawson’s five steps of realist review (clarifying scope and drafting an initial programme theory; identifying relevant studies; quality appraisal and data extraction; data synthesis; and dissemination of findings), we begin by developing an initial programme theory using the references of a scoping review on the oral health of refugees and asylum seekers and through hand searching in Google Scholar. Following stakeholder validation of our initial programme theory, we will locate additional evidence by searching in four databases (Ovid Medline, Ovid Embase, Cochrane Library and Cumulative Index to Nursing and Allied Health Literature (CINAHL)) to test and refine our initial programme theory into a middle-range realist programme theory. The resultant theory will explain how community-level oral health promotion programmes for humanitarian migrants work, for whom, in which contexts and why.Ethics and disseminationSince this study is a review and no primary data collection will be involved, institutional ethics approval is not required. The findings of this study will be disseminated in peer-reviewed journals, local and international conferences, and via social media.Trial registration numberCRD42021226085.