Abstarct: Social capital has been considered increasingly by authorities of different areas of science, especially management, in recent years. In the other hand, remedial organizations such as hospitals can improve their effectiveness and efficiency through establishing, reinforcing, and distribution of this valuable and untouchable capital. In addition, organizational leadership style is an important factor in organizations subjects. A new theory for leaderships is transformational leadership. The present thesis tries to investigate the relationship between transformational and transactional leadership and social capitals in Sari's hospitals. The research method is descxriptive – correlation. In terms of goal, this research is considered as an applied one. We also used a structural model especially procedural analysis. The statistical population includes all remedial employees of Sari's hospitals totally amounting 2000 people. baxsed on Morgan table and random sampling a number of 322 employees were selected as sample. Assessment tools include: Bass& Avolio multi- variable leadership questionnaire (2000), and organizational social capital questionary. Validity of said questionnaires is 87% and 93%, respectively. In this research, we investigate the relationship between dimensions of transformational and transactional leadership with social capital's definitions: cognitive, relative, and structural capital. Analysis was carried out by using the Pearson correlation coefficient, multiple regressions by SPSS21 and SEM by LISREL9.1. Our assumptions were confirmed with the results. The relationship between transformational leadership and social capital is meaningful and positive. In addition, the relationship between transactional leadership and social capital is meaningful and negative.