Responsible leadership style is formed based on the common concepts and ideas of organizational responsibility, ethical and legal leadership. At the same time, competent personnel play a vital role in sharing information to mutually help each other achieve performance goals. The aim of this study is to investigate the effect of responsible leadership on knowledge sharing behavior with regard to the mediating role of individual-organization fit and the moderating effects of organizational culture among employees of the Social Security Organization. The statistical population of this study is the employees of the Social Security Organization of Khorasan Razavi Province. The data collection tool of this study is a standard questionnaire. Structural equation modeling with PLS-Smart software was used to test the hypotheses. The research findings showed that responsible leadership has a positive and significant effect on the individual-organization fit and knowledge sharing behavior of employees of the Social Security Organization of Khorasan Razavi Province. Also, individual-organization fit plays a mediating role in the relationship between responsible leadership and employees' knowledge sharing behavior, and organizational culture positively and significantly moderates the relationship between responsible leadership and individual-organization fit. Based on this research, it can be stated that a manager with a responsible leadership style can improve and promote employees' knowledge sharing behavior by considering organizational culture through the impact it has on employee communications and their constructive job relationships.