In this study, 8 field surveys of the vascular plants in Naejangsan National Park were conducted between May and November 2021. The vascular plants identified comprised 424 taxa, made up of 98 families, 257 genera, 377 species, 8 subspecies, 34 varieties, and 5 forms. Among these, 12 taxa of plants endemic to Korea, including Vicia hirticalycina Nakai and Ajuga spectabilis Nakai, were identified. Threatened plants according to the IUCN Red List Categories were 4 taxa consisting of 3 taxa of Vulnerable (VU) (Lycoris chinensis var. sinuolata K.Tae & S.C.Ko, Iris koreana Nakai, and Cymbidium macrorhizon Lindl.), and 1 taxon of Near Threatened (NT) (Cremastra appendiculata var. variabilis (Blume) I.D. Lund.). Three taxa (including L. chinensis var. sinuolata) des ignated as Endangered Wildlife Class II were also recorded. Floristic regional indicator plants included 18 taxa, 3 of which were Degree V and 15 were Degree III. In total, 21 taxa were recorded as alien plants, resulting in a naturalization index of 4.95% and an urbanization index of 6.54%. Additionally, 1 taxon of an ecosystem-disturbing plant was identified; namely, Humulus japonicus Siebold & Zucc.