Principals play a very important role in determining the quality of education in schools. The success of the principals to mobilize all potential in the school environment is highly dependent on the leadership styles. Job satisfaction and organizational commitment of the principals, teachers and administrators are considered as indicators in determining the success of the school institution. The objective of the research was to investigate the role of job satisfaction as a mediator in influencing the directive and participative leadership styles toward the elementary school principal organizational commitments in Medan. The sample of the research was 164 junior high school principals of the school principals selected and the data analyzed with path analysis. The results showed that (1) the principal job satisfactions did not function positively as a mediator between directive leadership styles and organizational commitments, (2) job satisfaction found as a positive mediator between participative leadership styles and principal organizational commitment.