This study was conducted with the aim of assessing the diversity of medicinal plants in Lai Son Island, Kien Giang province, which is a scientific basis for more effectively using, managing, and preserving this medicinal plant resource in this province. In this study, the PRA (Participatory Rural Appraisal), field investigation, morphological comparison, and classification, with the aid of specialized medicinal plant books were used. The results showed a total of 353 species of medicinal plants belonging to 264 genera of 112 families in 4 divisions. Among them, Magnoliophyta was the most diverse division with 94.90% % species, 95.08% genera, and 90.18% families. Seven species were listed in “Red List of Vietnamese medicinal plants” (2006), “Vietnam Red Book” (2007), and the Decree 06/2019/ND-CP. The medicinal plant species were divided into ten life forms and distributed in six biotopes. The most species diversity was recorded in the natural forest on rocky mountain biotope. Ten parts of plants were used to medicate 36 disease types. Twenty-four species were commonly used by local people.