In this study, we describe a green pit viper of the genus Trimeresurus Lacépède, 1804, from Yunnan Province, China, based on both morphological and molecular evidence. Morphologically, the new species can be distinguished from other congeners by a combination of the following characteristics: (1) dorsal body grass-green, ventral body yellowish green; (2) postocular stripe absent in females; (3) ventrolateral stripe white, present on the first dorsal scale rows in females; (4) iris golden yellow in females; (5) DSR 19/20–19–15 ( N = 2), VEN 145–147 ( N = 2), SC 55–60 ( N = 2); (6) 10–11 cephalic scales; (7) first supralabial separated from the nasal scale by a distinct suture. Phylogenetic analysis based on the mitochondrial cyt b , ND4, 12S rRNA, and 16S rRNA gene fragments indicates that the new species is genetically divergent from all congeners (BPP 1.00/UFB 100), with uncorrected genetic distances of the mitochondrial gene cyt b ranging from 3.6% ( T. mayaae ) to 13.1% ( T. hageni , T. septentrionalis , T. guoi , and T. ayeyarwadyensis ) compared with its congeners.