Trivalvaria tomentosa sp. nov. is herein described from Yunnan Province in China. It is easily distinguished from all previously described Trivalvaria species by having tomentose twigs, petioles, abaxial surface of the leaves, sepals and petals. A detailed description for the new species, along with line drawings, photographs, as well as morphological comparisons with similar species, are provided. A phylogenetic analysis was conducted to confirm the placement of this new species within Trivalvaria.