Introduction: This study was conducted to investigate the relationship of personality traits (conscientiousness and neuroticism) and organizational characteristics (job characteristics, organizational justice, person-job fit and organization - based self-esteem) with work motivation.Method: Participants included 225 employees of the Lorestan National Oil Products Distribution Company (NOPDC). The instruments used in this study included the Work Motivation Scale, the NEO-Five Factor Inventory (NEO-FFI), the Job Diagnostic Survey (JDS), the Organizational Justice Questionnaire, the Person-Job Fit Scale and Organization-Based Self-Esteem Scale.Results: Results indicated that conscientiousness, job characteristics, organizational justice, person-job fit and organization - based self-esteem were positively related with work motivation and neuroticism was negatively related with work motivation. Moreover, hierarchical regression analysis revealed that predictor variables (conscientiousness, job characteristics, organizational justice, person-job fit and organization - based self-esteem) account for 61 percent of the variance of work motivation.Conclusion: Regarding the relationships between predictor variables (conscientiousness, job characteristics, organizational justice, person-job fit and organization - based self-esteem) and work motivation, organizations should select employees with high score conscientiousness for increasing their work motivation and should focus on increasing organizational variables such as job characteristics, organizational justice, person-job fit and organization - based self-esteem in the workplace.