<p>Deviant workplace behaviour is a significant concern in law enforcement, where misconduct can undermine public trust and institutional effectiveness. This study investigates how work culture and perceived organizational injustice contribute to deviant behaviour among personnel in a national law enforcement agency, and whether work engagement moderates these relationships. The research draws on organizational justice theory and integrates cultural dimensions using the Competing Values Framework to explore how structural norms, fairness perceptions, and psychological states interact in a hierarchical policing environment. A total of 417 officers from 16 police districts participated in the study. Validated instruments were translated and adapted for cultural relevance, and data were analysed using multiple and hierarchical regression techniques. Results showed that adhocracy and hierarchy cultures were negatively associated with deviant behaviour, while market culture and perceived injustice were positively associated. Clan culture, which emphasizes shared values and interpersonal support, showed no significant effect. Its lack of influence may reflect contextual limitations or the dilution of clan principles in mixed cultural environments. Perceived injustice emerged as a strong independent predictor, particularly in areas related to favouritism, inequitable punishment, and lack of recognition. Work engagement moderated the relationship between adhocracy culture and deviance, with a stronger protective effect observed under low engagement conditions. However, engagement did not moderate the link between perceived injustice and deviance, suggesting that in rigid institutional settings, engagement may not buffer the behavioural consequences of unfair treatment. The coexistence of high engagement and deviance among some officers points to a possible disconnect between task performance and emotional alignment, highlighting the complexity of behavioural regulation in command-driven environments. These findings underscore the importance of cultivating participatory cultures, promoting fairness through transparent policies, and fostering meaningful engagement to reduce misconduct. While the study is context-specific and cross-sectional, it offers valuable insights for institutional reform and contributes to broader efforts to build effective, accountable, and inclusive public institutions.</p>