Background: Available epidemiological data suggest that a significant proportion of migrants from sub-Saharan Africa living with HIV in Europe were infected after their arrival, although the exact proportion is unknown. Materials and methods: We estimated the proportion of sub-Saharan migrants who acquired HIV after arriving in France by combining biographical and clinical data collected from a representative sample of patients born in sub-Saharan Africa and followed for HIV infection in hospitals in the Île-de-France region. Infection was considered to have been acquired in France if any of the following biographical criteria were met: 1) a duration of stay in France prior to diagnosis of at least 11 years, 2) a negative HIV test after arrival in France, 3) first sexual intercourse after arrival in France. When none of these criteria were met, we estimated the time since infection based on the first CD4 count using a statistical model of CD4 decline. This duration was estimated 500 times for each participant. We considered that infection had occurred in France if at least 50% (in the median scenario) or at least 95% (in the conservative scenario) of the 500 estimated durations were shorter than the duration of residence in France. Results: Among 898 HIV-infected adults born in a sub-Saharan African country, we estimated that 49% [95% CI: 45–53] of them in the median scenario and 35% [31–39] in the conservative scenario acquired HIV after arriving in France. This proportion was lower for women than for men (30% [25–35] vs. 44% [37–51] in the conservative scenario) and increased with the length of stay in France. Conclusion: Given this significant proportion of migrants from sub-Saharan Africa who became infected with HIV after migration, it appears necessary to improve prevention efforts among this population group and, to that end, to better understand the determinants of these infections occurring in France.