Wetlands provide critical regulating ecosystem services, including the attenuation of storm water runoff and mitigation of urban flooding, yet rapid urbanization in many African cities has led to significant wetland degradation with poorly understood consequences for flood risk. This study examined the role of wetlands in flood regulation, using Nakivubo Wetland in Kampala City as a case study, guided by objectives assessing the wetland’s ecological condition and spatial extent, its hydrological functions, the relationship between its degradation and flooding, and the drivers of its degradation. A descriptive case study design integrating remote sensing/GIS land cover change analysis with household surveys (n = 103), key informant interviews, and field observation was employed. Land cover analysis showed a 42.0 percent loss of papyrus-dominated wetland vegetation between 1993 and 2023, accompanied by a 276.0 percent increase in built-up area. Households nearest the most degraded sections of the wetland reported significantly more frequent flooding (mean = 4.10 episodes/year) than those near better-preserved sections (mean = 0.95 episodes/year). Wetland vegetation loss was strongly correlated with flood frequency (r = 0.710, p < 0.01), and regression analysis showed vegetation loss and distance from the wetland edge jointly explained 59.9 percent of the variance in flood frequency (R² = 0.599). Path analysis confirmed that the erosion of the wetland’s water storage and attenuation capacity partially mediates the relationship between vegetation loss and flooding, with a significant indirect effect (β = 0.340, p < 0.01) in addition to a significant direct effect (β = 0.481, p < 0.01), producing a total effect of 0.821. The study concludes that continued encroachment, weak enforcement, and solid waste dumping have substantially compromised the wetland’s natural flood regulation function, and recommends strengthened enforcement, wetland restoration, improved solid waste management, and the integration of wetland conservation into citywide drainage planning.