During a survey of ascomycetes in Yunnan in the dry season (April 2021), an ascomycete was found on para grass [Brachiaria mutica (Forssk.) Stapf] submerged in a freshwater stream in Mengla County, Xishuangbanna Dai Autonomous Prefecture, Yunnan Province, China. Multi-locus phylogenetic analyses of combined ITS, LSU, SSU, tef1-α and rpb2 gene regions demonstrated that the novel strain (KUMCC 21-0469) shared the same branch length with Occultibambusa jonesii [GZCC 16-0117, ex-type strain] (98% ML, 1.00 PP) and grouped with O. aquatica with signifi cant support (91% ML, 1.00 PP). Morphological characteristics were inadequate to distinguish species in Occultibambusa. We therefore identify our new collection (KUN-HKAS122243, strain KUMCC 21-0469) as O. jonesii based solely on phylogenetic evidence. The conspecifi c status of O. aquatica and O. jonesii is questionable in this study due to the lack of genetic information on O. aquatica. The ex-type stain of O. aquatica has been acquired to be re-sequenced for further evaluation of its phylogenetic status. Occultibambusa jonesii was isolated from dead culms of bamboo in terrestrial environments in Guizhou Province, China. In the present study, the species was isolated from para grass submerged in a freshwater stream in Yunnan Province, China. This discovery is a new record on host/habitats and geography for O. jonesii. Detailed description and illustration of O. jonesii as well as the updated phylogenetic relationships of taxa in Occultibambusaceae and geographical distribution map of Occultibambusa are provided.