The purpose of this study was to investigate the influence of personality traits on the expanded model of organizational identification and to empirically address the following question: "can personality traits explain why some people identify strongly with their organization more than others?" The population of this survey included employees of the Iranian Ministry of Science, Research and Technology. The research method adopted in this study was survey and the main tool for data collection was questionnaire. The results indicated that there were significant positive relationship between personality and organizational identification, significant negative relationship among personality, disidentification and neutral identification, and no relationship between personality and ambivalent identification. It was also found that highly extrovert employees with agreeableness traits, identified with their organization more than those with neuroticism trait, and neurotic employees felt more disidentification, neutral, or ambivalent identification.