Forensic psychology in Nigeria is a relatively underdeveloped field with limited empirical research examining psychological factors influencing criminal behaviour. A systematic review of published articles from major Nigerian academic databases was conducted, with a focus on qualitative and quantitative studies that have explored psychological factors related to crime. The analysis revealed a significant proportion (45%) of criminal cases involving mental health issues, particularly substance abuse and personality disorders, which are underreported in official records. This study highlights the importance of integrating forensic psychology into Nigeria's legal system to improve case outcomes and offender rehabilitation efforts. Policy recommendations include incorporating psychological assessments as part of criminal justice processes, enhancing mental health services for offenders, and promoting public awareness campaigns on mental health in crime prevention. Forensic Psychology, Criminal Behaviour, Nigeria, Psychological Factors