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Introduction: Effective Leadership is an essential factor for success of an organization. In new century, it is believed that using transformative leadership style by managers cause increase of organizational commitment by the employees. Therefore, this research is aimed to determine the relationship of transformative leadership style of managers with organizational commitment of employees in Tehran University of Medical Sciences [TUMS] at 2015

Methods: The study was a cross - the cross on the 70 managers and 225 staff were made at various levels. Multifactorial questionnaire transformational leadership and organizational commitment Allan Mayer questionnaire was used. To calculate descriptive statistics such as mean and standard deviation and analytical tests such as t-test, and Pearson correlation coefficient was used statistical software SPSS version 19

Results: The headquarters managers had desired transformative leadership style, and also the employees had moderate organizational commitment. Moreover, There was significant relationship between the managers' transformational leadership style with employees' organizational commitment [P=0.007]

Conclusion: Concerning with significant relationship between transformative leadership style with organizational commitment, it is expected that with paying attention to using transformative leadership, it is used for selection of headquarters managers in order to improvement of the employees organizational commitment as an one of the important factor