A new agaric species, Entoloma mengsongense, is described and illustrated from samples collected in Mengsong, Yunnan Province, China. Microscopic observations were carried out to describe the micro- and macromorphological characteristics of specimens, and molecular identification was performed to verify the novelty of the species. The species is mainly recognized by its conical to plano-concave pileus, with yellowish brown fibril and 4-8 x 4-6 mu m sized, cuboid-quadrate basidiospores. Molecular phylogenetic analysis using ITS sequence data also indicated that this is a new species closely related to E. virescens and E. hochstetteri. Morphological and molecular phylogenetic differences separate E. mengsongense from all other known species of Entoloma.