While taxonomic research of the genus Diploderma has made considerable progress in the past decade, far less attention was given to the arboreal species in the subtropical areas. Combining mitochondrial genetic and morphological data, we evaluated the current taxonomic hypotheses of one of the subtropical, arboreal species complexes, the D. fasciatum complex, based on examination of the type series and newly collected specimens. Mitochondrial genealogy shows that D. jinggangense, D. fasciatum, and D. szechwanense together form a monophyletic group, and D. jinggangense is paraphyletic to D. szechwanense. Although there are moderate genetic divergences among populations, such divergence differences are gradual geographically. Morphological comparisons of all commonly used diagnostic characters fail to differentiate the three species. In particular, the previously proposed diagnosis, the presence of transverse gular fold, is variable in this species complex. Our data support the previous taxonomic hypothesis that D. szechwanense and D. fasciatum are synonyms, and we also add D. jinggangense as another junior synonym of D. fasciatum. With newly available specimens, we revise the diagnostic characters of D. fasciatum, describe its coloration in life, and expand its distribution in southwestern and southern China. Our discovery of D. fasciatum in Guangdong Province represents a new provincial herpetofauna record. Finally, we highlight the taxonomic uncertainties on the species status of D. grahami with respect to D. fasciatum and discuss the issue on the recent unnecessary changes of the Chinese common names of the genus Diploderma, recommending maintaining stability of Chinese common names and continuous usage of “Long Xi” as the common name for Diploderma.