Managerial psychology can benefit human resource management in Nigeria's civil service. It helps HR managers better understand employee behavior, develop organizational culture, and address deviant behavior. The study will use qualitative analysis including literature review and interviews to examine the impact of managerial psychology. Data will be analyzed statistically and presented visually to identify trends in its benefits according to participants. Ethical considerations like confidentiality and informed consent will be followed. Managerial psychology can enhance relationships, cultural adoption, and handling of deviant behavior to help HR managers achieve organizational goals and strategies.