Background One of the classic challenges for prevention programmes is reaching the populations they serve. In France, a substantial number of African migrants living with HIV acquired their infection after migrating. The aim of this paper is to better understand the characteristics of the population reached by a community-based outreach approach. Methods We compared sociodemographic characteristics across three different groups in the Paris greater area: (1) the general African migrant population (Population census), (2) the African migrant population using either the regular healthcare system or the system for vulnerable populations (PARCOURS Survey) and (3) the African migrant population reached through a community-based mobile unit (Afrique Avenir). Comparisons were conducted according to sex, age, region of origin, duration of residence and occupational and legal statuses using χ 2 tests. Results The migrants reached by the mobile unit were mostly men (69%), 52% of whom were younger than 35~years old. They more often lived in precarious situations than did the general sub-Saharan population (49% vs 35% were unemployed, respectively, p<0.001) and the ones accessing the regular healthcare system. Fewer of them lived in precarious situations than did migrants seeking healthcare consultations for vulnerable populations (42% in the mobile unit vs 54% in healthcare consultations were undocumented, p<0.028). Conclusion Our study shows that the outreach approach can constitute a missing link in the prevention chain among sub-Saharan African migrants, reaching a group that differs from the general migrant population and from the migrant population in healthcare services\textemdash not only the newly arrived migrants who live in more precarious situations but also those who have been in France for several years and are still affected by social hardship.