A study of fish species abundance of Otammiri River, Owerri, Nigeria was conducted from April to August, 2012. Four hundred and three (403)fishes belonging to 10 families, 16 genera and 21 species were collected from artisanal fishers using various fishing gears. The fish samples were taken to laboratory, identified, counted and their weights and lengths measured. The unnamed cichlid species ranked highest in percentage number and weight as well as Index of Preponderance (38.7%, 33.6% and 51.1% respectively), while the least were Polycentropis abbreviata, Hepsetus odoe, Synodontis omias, Chrysichthys aluensis and Chrysichthys furcatus each constituting 0.2% of the total number of fish collected. Among fish families, Cichlidae ranked highest in percentage number (82.63%) and weight (81.2%), followed by Hepsetidae (5. 7% and 8.0%) and Anabantidae (4.47% and 2.8% respectively). The least were Characidae, Notopteridae and Mochokidae. The presence of an unnamed fish species in the river is an indication that there could be more unknown aquatic living resources with strong potential benefits to the River. The information provided in this study reflects the potential of the fish resources of Otammiri. This will serve as invaluable baseline tool in fisheries management planning and policy formulations that will enhance the development of fisheries in the area