Many organizations have adopted enterprise resource planning (ERP) systems in recent years to integrate information and information-based processes within and across functional areas. Because of the under-utilization of ERP systems, most of these organizations are disappointed in reaching the anticipated business goals. It is imperative to explore how to facilitate the usage of ERP systems for organizations. This study aims to develop an understanding of the effect of knowledge sharing on ERP system usage and the factors affecting employees' knowledge sharing after the initial implementation of an ERP system. Selected social oriented theories were employed to develop our conceptual model. By means of a survey of 804 ERP users from 53 Taiwan companies, we confirmed our research model to some extent and found that social capital, intrinsic motivation, and self-efficacy all have significant impacts on knowledge sharing. However, contrary to common belief, we found a negative, though insignificant, effect of extrinsic motivation on knowledge sharing. The implications for research, practice, and future research directions are discussed herein.