Background and Objectives: Although crucial role of social determinants on health is well known; such as precarious living conditions, some underserved population remains under-investigated in France such as Gypsies and Travellers. We aimed to describe for the first time in France, Gypsies and Travellers’ living conditions – including environmental exposure, and factors associated with their health status and their access to healthcare and prevention. Methods: A cross-sectional study with a three-stage random sample design (living area, household, individual) was conducted between October 2019 and March 2022, in Nouvelle-Aquitaine. Trained social workers administered face-to-face questionnaires to collect data on adults and children including demographics and socioeconomic situation, living conditions, mobility, health status and access to healthcare and prevention (vaccination, screening, literacy). Anthropometric measurements, vaccination records and environmental exposure questionnaire were also collected. Results: 1030 adults and 337 children were included with a very high participation rate (73.6%). For children, 77.8% had full measles-mumps-rubella vaccination coverage, 16.2% were overweight and 7.6% suffered from behavioural and emotional difficulties. Over 74% of the households had housing insecurity, 22.2% did not have a drinking water supply, and 43% were located less than 200 meters from a major road. 71.3% of the adults were overweight (including obesity), 14.4% reported diabetes, 24.7% hypertension, and 14.0% depressive disorder. The prevalence of depressive syndrome was significantly higher in adults living in precarious and unauthorized housing than in those with adequate housing (19.2 vs 14.7%, p=0,04). Concerning access to healthcare, 82.6% had visited a general practitioner in the previous year. Conclusions: Traveller children and adults faced deleterious environmental and living conditions potentially affecting their health and their access to healthcare and prevention. These Results demonstrate the need for urgent action targeting underserved populations, taking into account their specific needs.