Background: Workplace Deviance are among the most common phenomena observed in organizations. This might be attributed to narcissistic style of leadership and the manifestations of organizational aggression. It is further aggravated by increased workplace hostility. The main purpose of this research is to observe the impact of moderated mediation of organizational aggression and workplace hostility upon the relationship between narcissistic leadership and workplace deviance. Methodology: A cross-sectional investigation was conducted using self-survey method. With 673 participants in the study, the author used an electronic questionnaire (Google Forms) to collect data from employees working at five food product companies in Iraq. Mediation model, moderation analysis, and moderated mediation models were evaluated using Structural Equation Modeling (SEM) for which AMOS V.23 software was used. Results inferred that organizational aggression partially mediates a positive relationship between narcissistic leadership and workplace deviance. Further, the relationship between organizational aggression and workplace deviance depends on the changes in level of workplace hostility. Moreover, the study empirically supports the fundamentals of moderated mediation model. In other terms, the study infers that indirect effect of narcissistic leadership in workplace deviance through organizational aggression has been significantly moderated by workplace hostility. Conclusion: When leaders adopt narcissistic behaviors to achieve their personal interests, it leads to increased organizational aggression and workplace deviance that eventually increase the levels of workplace hostility. Accordingly, moderated mediation model provides a better understanding about how narcissistic leadership, organizational aggression, and workplace hostility all work together to influence workplace deviance.