This study aimed to investigate the impact transformational leadership on knowledge workers' organizational behavior citizenship in Iran’s National Oil Company. The research method was descriptive-correlative. 97 experts working at staff Units of Iran’s oil Company were selected, using census method. In order to collect data, two questionnaires were used.1- Bass and Avalio’s transformational leadership questionnaire (a=. /78), 2- Podsakoff’s OCB questionnaire (a=. /89). To analyze data, Pearson’s correlation and structural equation model were used. The finding showed that there was a positive relationship between organizational behavior citizenship with transformational leadership and its components: Idealized Influence, Inspirational Motivation, Intellectual Stimulation, and Individualized Consideration. The findings also showed that there was a positive relationship between all components of transformational leadership (i.e., Inspirational Motivation, Intellectual Stimulation, and Individualized Consideration) and components of organizational citizenship behavior (i.e., conscientiousness, courtesy, sportsmanship and altruism). The finding structural equation model showed that transformational leadership impact on organizational behavior citizenship in Iran’s National Oil Company. key word: transformational leadership , organizational behavior citizenship, Idealized Influence, Inspirational Motivation, Intellectual Stimulation, Individualized Consideration, Iran’s National Oil Company key word: transformational leadership , organizational behavior citizenship, Idealized Influence, Inspirational Motivation, Intellectual Stimulation, Individualized Consideration, Iran’s National Oil Company key word: transformational leadership , organizational behavior citizenship, Idealized Influence, Inspirational Motivation, Intellectual Stimulation, Individualized Consideration, Iran’s National Oil Company