Four species of the genus Karstsinnectes, which live in dark, low-energy groundwater ecosystems, are currently recorded, mainly distributed in the upstream of the Pearl River, the Youjiang River and the Hongshui River. Completing biodiversity surveys is particularly difficult due to the particular cave habitats inhabited by these species. In this work, we describe a new cave fish of the genus Karstsinnectes, namely K. cehengensis Luo, Zhao & Zhou, sp. nov., collected from the Beipanjiang River, the upstream of the Hongshui River. Genetically, the four individuals of the new species form a phylogenetically separate lineage, as the sister clade of K. acridorsalis, with a 9.4–9.5% genetic difference in mitochondrial Cyt b. Morphologically, the new species can be distinguished from its congeners by a combination of the following morphological characteristics: body naked, without body color; eyes reduced, diameter 1.4–3.8% of head length; anterior and posterior nostrils adjacent, anterior nostril not elongated to a barbel-like tip; lateral line incomplete; caudal fin forked; dorsal-fin rays iii-7, pectoral-fin rays i-11–12, pelvic-fin rays i-7, anal-fin rays iii-5, with 14 branched caudal-fin rays. The discovery of this new species represents the northernmost distribution of species within the genus Karstsinnectes and the first record from Guizhou Province. All currently known species of this genus inhabited in caves, making them ideal organisms for studying historical river connectivity and cave formation process.