Purpose The purpose of this paper is to analyze the effects of the psychological ownership of employees on organizational citizenship behavior as an organizational effectiveness and how do team-member exchange and perceived team support have moderating effects on the relationship between psychological ownership and organizational effectiveness. Design/Methodology/Approach Based on a survey method, the empirical analysis sampled 435 employees working at 5 MNC subsidiaries in South Korea. With the hierarchical regression analysis, all hypotheses were tested and supported. Findings This paper shows that the higher the psychological ownership, the greater the positive effects on the organizational citizenship behavior and it also reveals that organizational effectiveness could be affected by employee’s psychological ownership level. Team-member exchange and perceived team support have moderating effects on the relationship between psychological ownership and organizational citizenship behavior. Research Implications In the management of this paper, this study shows that an employee’s psychological status has an importance to explain their behavior and it should be recognized that the behaviors are affected by organizational context variables, at the team level, such as team-member exchanges and perceived team support.