Background and aims: Parque Interjurisdiccional Marino Costero Patagonia Austral is a protected area that is home to incredible biodiversity. Within the Park is Isla Valdes, an island whose vegetation is unknown and where European rabbits, an invasive herbivorous specie, have been introduced. The aims of this work are: a) to know the floristic richness of Isla Valdes; b) to evaluate the conservation status of its flora; c) to identify and characterize the different vegetation units; d) to analyze the differences and their possible causes between the vegetation units. M&M: the island was traveled around establishing the different vegetation units. Three transects were made in each one, using the Floristic -Holistic Method for arid, semiarid, and subhumid areas. With the data obtained, vegetation structure and ecological parameters were calculated, a list of the floristic composition was drawn up, each vegetation unit was described, and the current state of conservation of the vegetation was evaluated. Results: 74 species were identified, distributed in 31 botanical families. Five vegetation units with different floristic compositions and plant physiognomy were identified. 12 species are included in Argentina's preliminary red list of endemic plants, and two species have international conservation status (IUCN red list and CITES). Conclusions: The work constitutes the first floristic list of Isla Valdes, and provides important information for management decisions.