The study examined police in internal security management in Nigeria. The study covered the period of democratic or civil rule. The study made use of both primary and secondary data; the method of data collection was the quantitative data collection technique and the qualitative data collection technique. Content analysis and descriptive statistics were used to analyze the collected data. The results of the study revealed that corruption and terrorism are the dominant cause of insecurity in Nigeria; the police have not played a crucial role in the internal security management in Nigeria. The study also revealed that poor leadership, lack of orientation, distrust between the police and the public and inadequate training facilities are the major factors affecting the performance of police in managing internal security in Nigeria.