Increasing organizations and educational institutions have implemented virtual learning communities to encourage knowledge sharing. However, this task can not be accomplished simply by grouping people together and telling them "sharing your knowledge will make you learn better". This research attempts to examine the factors influencing knowledge sharing from the perspective of human behavior. Theory of Planned Behavior is integrated with social network ties and empirical findings from virtual learning community literature to develop the research model. The current research model comprises eight hypotheses to explore questions of whether social network ties, learners' attitude toward knowledge sharing, learners' beliefs of their capabilities in performing online knowledge sharing, and subjective norms relate to knowledge sharing intention, which leads to actual behavior in a virtual learning environment. This study empirically validates the hypothesized relationships using a field survey of college students and MBA students enrolling courses conducted in a virtual learning community. Attitude, subjective norm, Web-specific self-efficacy and social network ties are shown to be good predictors of knowledge sharing intention which, in turn, is significantly associated with knowledge sharing behavior. Knowledge creation self-efficacy does not significantly impact knowledge sharing intention. (Contains 3 tables and 2 figures.)