Exostoma kottelati, new species, is described from the Ranga River, Brahmaputra basin, in Arunachal Pradesh state, northeastern India. It differs from congeners in the Brahmaputra River basin in having a longer adipose-fin base (33.4–36.0 % SL vs. 23.4–32.9), a greater (except E. mangdechhuensis) pre-pelvic length (45.6–47.3 % SL vs. 39.3–44.6) and a greater pre-anal length (73.9–76.5 % SL vs. 62.2–70.1). It further differs from all known congeners by the following unique combination characters: the adipose fin is distinctly separated from the dorsal procurrent caudal-fin rays, pre-dorsal length 38.9–41.7% SL, adipose-fin base length 33.4–36 % SL, caudal peduncle length 18.7–21.1 % SL, caudal peduncle depth 8.8–9.5 % SL, and body depth at anus 12.5–13.5 % SL. This is the fifth species of Exostoma known from the Brahmaputra River basin.