Background Migration health research pays little attention to the places into which people migrate. Studies on healtheffects of contextual factors are often limited because of the ability of individuals to self-select their environment, butnatural experiments may allow for the causal effect of contexts to be examined. The objective was to synthesise theevidence on contextual health effects from natural experiments among migrant groups.Methods We performed a systematic review of natural experiments among migrant populations in PubMed/MEDLINE,The Cochrane Library, Web of Science, CINAHL and Google Scholar for literature published until 13 October2022. 5870 articles were screened in duplicate using the following inclusion criteria: quantitative natural experimentdesign, migrant population, context factor as treatment variable and health or healthcare outcome variable. Synthesiswithout meta-analysis was performed following quality appraisal using the EPHPP tool for quantitative studies anddata extraction (PROSPERO: CRD42020169236).Findings The 46 included articles provide evidence for negative effects of neighbourhood disadvantage on physicalhealth and mortality, while finding mixed effects on mental health. Articles comparing migrants with those thatstayed behind demonstrate detrimental effects of migration and adverse post-migratory contexts on physical healthand mortality, while demonstrating favourable effects for mental and child health. Natural experiments of policyenvironments indicate the negative impacts of restrictive migration and social policies on healthcare utilization,mental health and mortality, as well as the positive health effects when restrictions are lifted.Interpretation Natural experiments complement observational studies and provide robust evidence to advocate formore inclusive migration, health and social policies as well as neighbourhood improvement programmes. In order tostrengthen the methodological approach, future research utilising natural experiments should be more explicit in themechanisms underlying the experiment and provide details on potential causal mechanisms for the observed effects.