Skin parasitic infections are a common problem among homeless people. To estimate the prevalence of scabies and body lice among this population, two cross-sectional surveys based on random samples were conducted, one in public spaces in Paris and the other in various types of shelters in the Île-de-France region. A nurse administered a detailed questionnaire on sociodemographic characteristics, living conditions, hygiene practices, and healthcare utilization, followed by a dermatological examination. She took photographs of suspicious lesions for subsequent review by a dermatologist and inspected clothing for body lice. The prevalence of body lice was estimated at 5.4% among people sleeping in public spaces (95% CI: [1.7–9.1]) and that of scabies at 6.5% (95% CI:[0.5–12.5]), whereas among people sleeping in shelters, they were 0.15% (95% CI: [0.0–9.7]) and 0.4% (95% CI: [0.1–1.8]), respectively (p < 0.02 in both cases). In public spaces, after multivariate analysis, being female, citing squatting as one of the three main types of housing, and not owning a sleeping bag were significantly associated with a diagnosis of scabies. Similarly, still in public spaces, begging, a history of pubic lice, and not showering in public bathhouses are associated with having body lice. The identification of two subpopulations with different sociodemographic characteristics, specific lifestyles and hygiene practices, and varying prevalences of ectoparasitic infections should enable targeted prevention and awareness-raising efforts.