The fish composition of the three study sites of the reservoir were studied over a period of fifteen months (January, 2020 – March, 2021). A total of twenty-eight (28) fish species emanating from fourteen (14) families were obtained. The family Cichlidae was the dominant family with Oreochromis niloticus being the most abundant fish species while family Malapteruridae was the least with only 0.088% of the total abundance. Biodiversity indices of the study sites such as species richness ranges from 2.79-3.28, while species evenness ranged between 0.73 to 0.84, and diversity index revealed a range of 2.23-2.65. The Dadin-Kowa Reservoir has a rich ichthyofaunal composition which is facing challenges of structural collapse unless if management strategies are fully adopted. The host communities should be made integral components of aquatic resources management team. And other means of livelihood should be made attractive to reduce pressure on aquatic resources and deter possible biodiversity depressions.