Abstract: The fish diversity of Periyar originating as a natural spring in Kolli Hills is reported. A total number of 19 species of fish belonging to 15 genera and 9 families were collected.The percentage occurrence is 36.88 for Cyprinidase, Bagridae and Cichlidae constituted each by 15.8.Of the 19 species Ompok bimaculatus and Pseudeutropius atherinoides are endangered and Barilius bendelisis, Puntius sophore, Labeo calbasu and Mystus cavasius come under low risk nearly threatened (LRNT) category and Cirrhinus reba, Puntius conchonius, Mystus vittatus, Mystus bleekeri, Awaous guamensis, Clarius batrachus and Mastacembelus armatus are vulnerable species.