The ECHO study assesses knowledge, attitudes, and practices related to the COVID-19 pandemic and measures its impact on vulnerable individuals living in shelters in France, the vast majority of whom are foreign nationals. The first wave of this study was conducted in May and June 2020. Participants born abroad demonstrated good knowledge of COVID-19 symptoms and satisfactory adherence to prevention and management measures (testing, isolation). Factors associated with the adoption of recommended behaviors to combat the epidemic within this population include age, educational attainment, trust in official information, and concern about COVID-19. A significant proportion of people forgoing care for reasons unrelated to COVID-19, a significant deterioration in mental health, as well as in people’s socioeconomic situation (employment, food and administrative difficulties, etc.) were also observed.