Species of Tricholomopsis are known to be lignicolous and to cause white rot. Several collections of Tricholomopsis that grow near bamboo were sampled from southern China and morphologically could not be assigned to any known species of Tricholomopsis. Furthermore, phylogenetic analyses inferred from nuclear ribosomal internal transcribed spacer region (ITS) and the D1-D2 domains of the 28S rDNA large subunit indicated that it is an independent lineage with undescribed species. As a result of morphological data and phylogenetic analyses the new lineage is formally described as T. rubroaurantiaca. This species is characterized by its light orange to yellowish orange squamulose pileus with reddish disc, mostly clavate-shaped cheilocystidia, absence of pleurocystidia, subglobose to broadly ellipsoid basidiospores 5.0–5.8 × (4.0–)4.3–5.0 μm, a cutis-type pileipellis, and is usually habitat with bamboo. Morphological description, color photos, phylogenetic placement and phenotypic comparison with the closely related taxa within the genus are presented.