Motivating people to contribute knowledge has become an important research topic and a major challenge for organizations. In order to promote knowledge-sharing, managers need to understand the mechanism that drives individuals to contribute their valuable knowledge. Several theories have been applied to study knowledge-sharing behavior. However, the research settings and findings are often inconsistent. In this study, we use the social exchange theory as our base to develop an extended model that includes IT support and organizational type as moderators. A meta-analysis on 29 reported studies was conducted to examine how different factors in the social exchange theory affect knowledge-sharing behavior. The findings confirm that the social exchange theory plays an important role underlying individuals’ knowledge-sharing behavior. The results also demonstrate that social interaction and trust derived from the social exchange theory and moderated by IT contextual factors can predict individual’s knowledge-sharing behavior.