The purpose of this research was mainly to examine the knowledge and practice of leaders on transformational leadership in ethio telecom at the head quarter in Addis Ababa. Sequential explanatory research design with quantitative method supported by qualitative data was used in this research. In this research standardized Multifactor Leadership Questionnaires, MLQ (5X-Short Form), was used to gather data from leaders and supervisors. Stratified random sampling technique was employed to select leader and supervisor respondents. The findings of leadersâ€™ responses revealed that they have the knowledge and practice of transformational leadership style in their leadership activities. But Supervisor respondents and leaders who were involved in the interview depicted that transformational leadership was not well understood and practiced by ethio telecom leaders. Moreover, there is no specific leadership style shared by all leaders in ethio telecom. In general, although transformational leadership has vital role in better involvement of employees and achievement of organizational goal, it was concluded that leaders were not practicing transformational leadership in the expected level in ethio telecom at head quarter. Finally, recommendations were suggested on the need of conducting regular in service training to leaders at all levels to improve their capacity to the highest level of transformational leadership and to equip them with appropriate leadership skills and competencies. The need to practice a common and shared leadership style to be emphasized by the top leadership and regularly communicated to all actors is recommended.rnKey words: Knowledge, Leadership, Transformational Leadership Style