Abstarct: During the past four decades, the impact of leadership styles on organizational performance has been a topic of interest among academics and practitioners. But there were always missing lixnks in studying leadership-performance relationship. Findings of studies reviewed suggest that transformational leaders who communicate an inspirational vision and provide intellectual stimulation are best associated with organizational effectiveness in organization. In recognizing these missing lixnks, we select a pair of mediating variables which – as the past research shown – are more consistent with the nature of organizations. Thus, the main objective of this research is to examine mediating effects of empowerment of employers and organizational commitment on the relationship between transformational leadership and organizational performance. To do that, divisions of Shahid Hasheminezhad Gas Processing Copmany in Iran’s petroleum industry has been chosen as the case study. Questionnaires were used for obtaining necessary information; SPSS and Lisrel used for information analysis. Research findings shows that transformational leadership has direct effect on performance of studied personnel; but empowerment of empolyers introduced as a moderator and intermediate leadership-performance relationship. On the other hand, organizational commitment didn’t show any effect on performance which is opposed to past research. Our suggestion for further research is to investigate intervening variable(s) in commitment-performance relationship of studied or similar organizations.