Nigeria’s aquatic ecosystems are currently under threat of localized or widespread physical, organic, and biological pollution. Therefore, the relationship between pollution status of water bodies and fish assemblage was investigated for Ekole river in the Niger Delta, Nigeria. This was done to gauge the seasonality of the pollution status of this important rivers and the effect it has on fish assemblage patterns. This is critical to forestall further pollution and safeguard food security. Sampling was done monthly for one year for physicochemical parameters from three sampling points on Ekole river. Physicochemical samples were analyzed for Dissolved oxygen (DO), Biochemical oxygen demand (BOD5), Temperature, Alkalinity, Electrical conductivity (EC) and pH using standard procedures. Fish samples were also collected monthly from fish landing points from fishers, counted and identified using standard keys. Data were analyzed for means and standard deviations. T-test was employed to check for similarities and variations between seasonal physicochemical parameters in the river system. Analysis was aided by the use of SPSS® version 20.0 software tool kit. Result show that there are no significant seasonal differences (P>0.05) in, BOD5. However, there are significant differences (P<0.05) in pH, DO, Temperature, Alkalinity and EC in the river. All physicochemical parameters of the river were within the international permissible limit. Fish data show that Ekole river has 20 families (29 species) with 12,406 individuals. The distribution and abundance of fish in Ekole river show that the wet season (6,740) has a greater species abundance than the dry (5,666) season. The families Cichlidae, Claridae, and Cyprinidae were the most dominant family in the river body. Based on the findings of this study, the water body is not under any immediate threat of pollution. It can be concluded that river system has acceptable water quality characteristics and healthy fish assemblage patterns.