Background: Although migrants constitute an important proportion of the European population, little is known about migrant sexual health. Existing research mainly focuses on migrants' sexual health risks and accessibility issues while recommendations on adequate sexual health promotion are rarely provided. Hence, this paper explores how refugees, asylum seekers and undocumented migrants in Belgium and the Netherlands define sexual health, search for sexual health information and perceive sexual health determinants. Methods: Applying Community-based Participatory Research as the overarching research approach, we conducted 223 in-depth interviews with refugees, asylum seekers and undocumented migrants in Belgium and the Netherlands. The Framework Analysis Technique was used to analyse qualitative data. We checked the extensiveness of the qualitative data and analysed the quantitative socio-demographic data with SPSS. Results: Our results indicate that gender and age do not appear to be decisive determinants. However, incorporated cultural norms and education attainment are important to consider in desirable sexual health promotion in refugees, asylum seekers and undocumented migrants in Belgium and the Netherlands. Furthermore, our results demonstrate that these migrants have a predominant internal health locus of control. Yet, most of them feel that this personal attitude is hugely challenged by the Belgian and Dutch asylum system and migration laws which force them into a structural dependent situation inducing sexual ill-health. Conclusion: Refugees, asylum seekers and undocumented migrants in Belgium and the Netherlands are at risk of sexual ill-health. Incorporated cultural norms and attained education are important determinants to address in desirable sexual health promotion. Yet, as their legal status demonstrates to be the key determinant, the prime concern is to alter organizational and societal factors linked to the Belgian and Dutch asylum system. Refugees, asylum seekers and undocumented migrants in ...