Isla de las Gaviotas is an island located in Río de la Plata estuary, Uruguay. The aim of this study is to determine and analyze plant species composition on this island and to identify vegetation zonation patterns. An angiosperm species list was generated using a qualitative sampling technique. We registered a total of 27 species, distributed among 18 families. According to species distribution patterns on the island, we propose four vegetation zones: North, Central, Southeast and West. Exotic species comprised 52% of the total number of species, reflecting a history of disturbance in the area. Nonetheless, this site also has a remarkable number of native species, in particular Heliotropium curassavicum, which is listed among Uruguayan species of conservation concern. Given that the loss of coastal plant species is a current problem, the proportion of native halophyte species recorded (37%) indicated the island’s importance as a relict of Uruguayan coastal vegetation.