In 2009, Brazil launched its National Program of Medicinal Plants and Phytotherapeutics, influenced by several international policies and agreements implemented in preceding decades. The program has sought to integrate the population's use of medicinal plants into the country's national healthcare system (O Sistema Único de Saúde, or SUS), preserve traditional populations' knowledge of medicinal plants, promote environmental conservation, and strengthen the country's pharmaceutical research sector. This program, along with other policies and federal initiatives regarding medicinal plants and traditional medicine, has affected populations within Brazil in varying ways, depending on geography, ethnicity, and other factors. The current study combines policy analysis and a total of nine months of ethnography to explore how Baixada Fluminense, a peri-urban region in the metropolitan area of Rio de Janeiro, acts as a space that presents complexities in how medicinal plant use is approached in policies. Case studies of a phytotherapeutic pharmacy and Afro-Brazilian religious groups examine how communities in the region interpret and operationalize policies about medicinal plants and traditional medicine. Research contributes to current discussions focused on defining and describing peri-urban areas in relation to ethnobiology, as well as discussions around the limits of national and international policies pertaining to medicinal plants and traditional medicine.