Knowledge sharing and utilization within organizations have been widely recognized as one of the factors affecting ERP system usage performance. Accordingly, the influence of absorptive capacity, which is closely related to knowledge sharing and knowledge transfer, on information system usage performance has attracted considerable attention from many researchers. Furthermore, the lack of organizational citizenship behavior leads to insufficient communication and interaction among members, which in turn reduces absorptive capacity and consequently has a negative impact on organization-wide knowledge sharing. Against this backdrop, this study pursued the following research objectives. First, it established a theoretical model of the relationships among organizational citizenship behavior, absorptive capacity, and ERP system usage performance, and empirically tested it. Second, it empirically verified whether absorptive capacity effectively mediates the relationship between organizational citizenship behavior and ERP system usage performance.