We examined the floristic composition and similarity of the Ponta do Tubarão Reserve of Sustainable Development, Diogo Lopes District, Macau, Rio Grande do Norte State, Brazil. During the Field Course of Ecology I and II of the Postgraduate Program in Ecology and Conservation of the State University of Paraíba (PPGEC-UEPB), herbarium collections of fertile specimens were made in the four recognized phytophysiognomies of the area; Caatinga, Dunes, Islands, and Mangrove. Our results were complemented by data from the speciesLink network. A total of 140 species, belonging to 102 genera and 47 families, were collected and identified. Four of the species are new records for the state of Rio Grande do Norte: Calliandra depauperata Benth., Calliandra spinosa Ducke and Bauhinia dubia G. Don (Fabaceae), which is also a new record for the Caatinga vegetation area, and Schultesia doniana Progel (Gentianaceae). Fabaceae was the most represented family with 23 species. Similarity analyses indicated three distinct vegetation groups, composed of the combined Dunes and Mangrove areas, the Island area, and the Caatinga area.