This study investigated the influence of personality traits on psychopathic behaviour among inmates at the Jos Correctional Center, Plateau State, Nigeria. Psychopathy, characterized by callousness, impulsivity, manipulativeness, and lack of empathy, remains a significant concern within correctional settings, particularly in Nigeria where empirical data on inmate populations remain scarce. Despite its well-documented prevalence in Western correctional contexts, the relationship between personality traits and psychopathic behaviour has received limited systematic attention within Nigerian forensic psychology. This study addressed that gap by examining how the Big Five personality traits; openness, conscientiousness, extraversion, agreeableness, and neuroticism predict psychopathic behaviour among incarcerated individuals, and by exploring gender differences in this relationship. A cross-sectional survey design was adopted. The study population comprised 300 registered inmates at Jos Correctional Center (Lamingo), from which a sample of 169 participants was selected using the Raosoft sample size formula at a 95% confidence level. The sample consisted of 147 males (88.0%) and 20 females (12.0%), with ages ranging from 18 years and above. Data were collected using two standardized instruments: the Big Five Inventory (BFI) for assessing personality traits and the Levenson Self-Report Psychopathy Scale (LSRP) for measuring psychopathic behaviour. Data were analyzed using simple linear regression, independent samples t-test, and multiple linear regression at a 0.05 significance level. Findings revealed a highly significant positive relationship between personality traits and psychopathic behaviour (β = 0.705, p < .001), with the personality traits accounting for approximately 49.7% of the variance in psychopathy scores. The independent samples t-test indicated a statistically significant gender difference in personality traits scores (t(105.452) = 11.636, p < .001). Multiple regression analysis further confirmed that personality traits and gender jointly and significantly predicted psychopathic behaviour (R² = .507, F(2, 164) = 84.180, p < .001). These findings underscore the critical role of personality in shaping psychopathic behaviour within Nigerian correctional settings and highlight the importance of gender-sensitive, personality-informed assessment and rehabilitation strategies.