The fish composition in the upper course of Otamiri River was investigated for six months between April and September 2019, to determine the related abundance and diversity of fish species in the river. Fish species were collected weekly using fishing gears from three sampling stations which were purposefully selected. Sixteen species of fish belonging to nine (9) fish families were recorded. Among the families, Cichlidae recorded the most abundant at 83.3%, followed by Notopteridae (6.7%), Alestidae (4.2%) and Clarotidae (3.8%). Others include: Hepsidae (0.4%), and Cyprinidae (0.2%), while Channidae and Gymnarchidae were recorded as the least abundance with values of 0.1% each. The study showed that Sarotherodon melanotheron has the highest diversity with the value recorded 3.18, followed by Coptodon zilli having the value 3.09 respectively. It also shows that Barbus occidentalis with the value 0.69, followed by Coptodon dageti with value 1.01 has the least diversity. The study also showed that Pelmatopia mariae with value 0.99 was highly distributed. From the study, the fish species harvested from this water body have low population. This has great implication on the stock in the fishery and can also act as an indicator of over-exploitation of this species. Regular and detailed study on species composition of this water body should be encouraged for the sustainable utilization of its resources, also a proper restocking of Otamiri water body should be embarked on by Imo State government to enhance fresh water fish availability in the State and its environs.