The present work was carried out in various sections of a stream in Sunderbani commonly known as Thandapani nallah in District Rajouri (J&K), to investigate its fish diversity and assemblage structure from January to December, 2013. Twelve species of fishes belonging to family Cyprinidae i.e. Schizothorax richardsonii, Tor putitora, Garra gotyla, Labeo boga, Labeo bata, Labeo dero, Crossocheilus latius, Puntius conchonius, Puntius sophore, Puntius ticto, Barilius bendelisis, Barilius vagra and one species of fish belonging to family Sisordae (Glyptothorax pectinopterus) were found. The relative abundance, dominance and diversity indices were also calculated. Station wise data in the order of dominance shows that in downstream at station 1st Labeo dero (17.85%) dominates whereas Tor putitora dominates (20.72%) at station 2nd (mid-stream) and Puntius conchonius (35.03%) dominates at station 3rd (upstream). The maximum fish diversity was reported in Station 1st with 12 number of species (40.43%, H = 2.141) followed by 6 species at Station 2nd (34.83%, H = 1.771) and minimum i.e. 5 species at Station 3rd (24.72%, H = 1.425).