As the current demand for more ethical, people-centered management, the interest in servant leadership should come as no surprise. Servant leadership, as proposed by Greenleaf (1977), is a leadership style that emphasizes the moral high ground of doing good to others now and into the future. Previous studies have demonstrated that servant leadership is positively related to followers’ job satisfaction and helping behavior. However, few of them have tested the psychological mechanism underlying these relationships, especially in Chinese context. Moreover, there is little research having considered the boundary condition under which servant leadership is effective. To fill these research gaps, this study proposed and examined a moderated mediation model of servant leadership in which prosocial motivational is a mediation mechanism and interactional justice is a moderation mechanism. Survey questionnaires were distributed among employees in five private companies located in Zhejiang Province. The final sample consists of 201 employees and 62 supervisors. The hypotheses on mediation and moderation were examined using hierarchical multiple regression. Further, the procedure developed by Preacher, Rucker and Hayes (2007) to assess moderated medication hypotheses. Results showed that servant leadership was positively related to follower job satisfaction and helping behavior, and prosocial motivation partially mediated these relationships. In addition, interactional justice moderated the relationship between servant leadership and followers’ prosocial motivation, such that the relationship was stronger when followers perceived higher level of interactional justice. Finally, moderated mediation analyses showed that prosocial motivation mediated the relationships between servant leadership and follower job satisfaction and helping behavior only when interactional justice was high. This study contributed to servant leadership literature in several ways. First, this study addressed the generalizability of servant leadership within China. The positive relationships between servant leadership and follower job satisfaction and helping behavior in the Chinese sample are consistent with the findings obtained from Western society. Second, from a social learning perspective, this study examined the mediation role of followers’ prosocial motivation in the effect of servant leadership on both follower job satisfaction and helping behavior. The finding added to our understanding of the process through which servant leaders exert their influence on followers. Finally, this study extended the existing knowledge on the effectiveness of servant leadership by clarifying its boundary condition. Results showed that interactional justice moderated the indirect effects of servant leadership on job satisfaction and helping behavior through prosocial motivation. The findings highlight the values of integrating research on servant leadership and justice, suggesting that servant leadership and interactional justice are most effective collectively.