The Azad Jammu and Kashmir is an area of high biodiversity, but very little is known about diversity of freshwater species. This research is conducted to examine the fish diversity of Poonch River Mahseer National Park, situated in Azad Jammu and Kashmir, Pakistan. The surveys are conducted from March 2020 to December 2020. Total 33 species are documented from Poonch River Mahseer National Park. Diversity indices showed that fish diversity of the Poonch river is rich (i.e. Richness, 7.203) and diverse, (i.e. Shannon-Weiner index =3.293, Simpson index=0.955). Evenness (i.e. 0.8161) is documented high. The research showed that the density of many fish species has decreased.