Abstract Ichthyofauna surveys in Diyung, Vomvadung, Khualzangvadung, Tuikoi, and Mahur rivers under Dima Hasao District of Assam resulted in the first report of 21 species of fish belonging to 19 genera, eight families, and four orders. These include Cypriniformes, Siluriformes, Synbranchiformes, and Perciformes. The species composition is highest in Vomvadung River with 11 species, followed by Diyung with eight species, Khualzangvadung with six species, Mohur with three species, and Tuikoi with two species. The conservation status of Systomus clavatus, Tor tor, Neolissochilus hexagonolepis, Neolissochilus hexastichus is near threatened, and Pterocryptis barakensis is endangered.