Records of the genus Niphargus are quite new in Iran. Recent investigations of subterranean cave-dwelling fauna revealed a diversity of new taxa, including several new niphargid species. All of these new findings have been recorded from the north and north-west of the country, in Alborz and Northern Zagros regions. This paper describes a cave species from the Central Zagros, the southernmost range border of the genus Niphargus. A full morphological description of the species, as well as a brief note on the ecology of the cave, is presented, along with a detailed comparison to morphologically related or geographically close species. The most distinctive characters of this species are its long and slender pereopod III-VII, no spine on the dorsal surface of the telson, and the short second article of the uropod III exopodite. These data suggest that this is a new species, N. keeleri sp. nov., which is named after the cave in which it was found in.