Employee financial corruption is one of the most significant challenges facing Iran’s administrative system, imposing substantial economic costs and undermining public trust in the government. This study aims to examine the impact of the extended Hexagon Fraud Theory dimensions (motivation, opportunity, rationalization, capability, arrogance, and collusion) on employee financial corruption, as well as to investigate the moderating role of the Big Five personality traits of the NEO model (neuroticism, extraversion, openness, agreeableness, and conscientiousness). The research is applied in purpose and descriptive in data-collection method, and the required data for testing the hypotheses were collected through a structured questionnaire. The statistical population consisted of employees working in the public sector, among whom384 questionnaires were distributed and collected. The reliability and validity of the instruments were examined and confirmed. The research hypotheses were analyzed using structural equation modeling (SEM) with Smart PLS software. The findings revealed that all six dimensions of the Hexagon Fraud Theory have a positive and significant effect on financial corruption. Moreover, the personality traits of conscientiousness and agreeableness demonstrated significant strengthening moderating effects, while neuroticism showed a significant weakening effect. The results indicate that the Hexagon Fraud Theory is an effective framework for explaining financial corruption among Iranian public-sector employees and can serve as a valuable foundation for policymaking in corruption prevention, high-risk employee screening, and anti-corruption training programs.