This study investigated the influence of Transformational and Transactional Leadership on teamwork and analyzed the mediating effect of self-efficacy and organizational commitment. For the analysis, a questionnaire survey was conducted on firefighting organizations that emphasized teamwork due to their job characteristics, and the collected data were analyzed using the structural equation. As a result of the analysis, first, it was found that transformational leadership had a direct positive effect on teamwork. Second, it was found that transactional leadership had a positive effect on self-efficacy, and transformative leadership had a positive effect on organizational commitment. Third, it was found that self-efficacy had a mediating effect in the relationship between transactional leadership and teamwork, and organizational commitment in the relationship between transformative leadership and teamwork. In other words, the more transactional leadership is demonstrated, the higher the sense of self-efficacy and the level of teamwork improves, and when the transformational leadership is demonstrated, the organizational commitment increases and ultimately the level of teamwork is improved. Taken together, leadership that is more effective in teamwork is transformative leadership, which can be seen as affecting teamwork through organizational commitment rather than self-efficacy. In addition, although the degree of relative influence is small, since transactional leadership improves teamwork through self-efficacy, leaders need to also consider transactional leadership to improve teamwork. This study is meaningful as a study that proves that transformational leadership and transactional leadership influence teamwork in a differentiated path by complementing insufficient teamwork research, using self-efficacy and organizational commitment as parameters.