The unique topography of North-East India and watershed pattern is an attractive field for Icthyological studies. This region has already recognized as a global spot of freshwater fish diversity. A great numbers of species have been reported from most of the North-Eastern region states. Subansiri River is the one of the major river of both Assam and Arunachal Pradesh. The present study on Icthyofaunal diversity of Subansiri River in Assam and Arunachal Pradesh was carried out from January 2011 to December 2011. Fishes are very important from the biodiversity point of view. The fishes are collected from the different parts of the river and the collected fishes were identified. A total 87 different fishes were collected under 55 genera; they are classified into 9 orders and 22 families. Cypriniformes dominates the whole river and found in higher numbers and Beloniformes and Tetradontiformes are found in less numbers. The River Subansiri is good potential of fish fauna.