Flooding is recurrent in Nigeria, occurring yearly at different scales. This geared the need for a study to reveal local government areas (LGAs) that are at risk and vulnerable to flooding. The multi-criteria approach was adopted, using geospatial techniques and data. Factors considered were elevation, slope, rainfall intensity, and distance to river. The factors were classified, reclassified, rated, and weighed in a systematic process. Nineteen states and 114 LGAs face high risks, especially communities in the Niger Delta, around the lagoons of Lagos, along River Niger, Benue, and the Cross-River. Also, 125 LGAs in 18 states face medium flood-risk vulnerability. Consideration the population density of communities, Lagos State is the most vulnerable because of LGAs with high population densities within high flood-risk zones. Other states with communities exposed to high flood-risk vulnerability include Rivers, Kogi, Cross River, Akwa Ibom, Anambra, and Delta. The study provides information key to proactive policy formulation, mitigation, and adaptation to flood risk in Nigeria.