This study investigates water quality trends in the River Niger Basin by analyzing samples collected from upstream (Sample A), midstream (Sample B), and downstream (Sample C) sites during the wet season. The water samples were analyzed at the Federal University of Technology (FUTMINNA), Chemistry Department laboratory. Key parameters, including temperature, turbidity, dissolved oxygen, and nutrint concentrations, exhibited notable variations along the river flow. Temperature decreased by 2.5 °C from upstream to downstream, while turbidity remained low despite slight fluctuations. Dissolved oxygen levels increased downstream, suggesting enhanced photosynthesis and aeration, whereas Biological Oxygen Demand (BOD) showed an initial decrease followed by a rise at the downstream site, indicating potential organic pollution. The pH level decreased significantly, indicating an increased acidification, while alkalinity rose, reflecting possible buffering effects. Nutrient levels exhibited complex dynamics, with variations in ammonia, nitrate, and phosphorus suggesting influences from urban runoff and nutrient cycling. These findings underscore the River Niger’s dynamic ecosystem and the need for continuous monitoring to manage water quality sustainably, highlighting the interplay of natural and anthropogenic factors affecting the aquatic environment.