Purpose – The purpose of this paper is to examine the impact mechanism of organizational culture (OC) on Enterprise Resource Planning (ERP) user’s explicit and tacit knowledge-sharing behavior in the context of enterprise systems usage. Design/methodology/approach – Drawing from social cognitive theory, the authors developed a comprehensive model that integrates OC, computer self-efficacy and employees’ knowledge-sharing behaviors. In total, 343 valid questionnaires were collected from ERP users of 115 firms and structural equation modeling technique was used to test the model. Findings – Empirical results suggest that hierarchical culture that focusses on efficacy and uniformity is positively related with employees’ explicit knowledge sharing; group culture that focusses on trust and belonging is positively related with employees’ tacit knowledge sharing, and their relationship is fully mediated by employees’ computer self-efficacy. In addition, computer self-efficacy also partially mediates the relationship between rational culture and employees’ knowledge sharing. Practical implications – This study provides guidelines for top managers to enhance employees’ computer self-efficacy and facilitate employees’ knowledge-sharing behavior by developing appropriate type of OC. Originality/value – This study unpacks the mediating mechanism between OC and knowledge sharing, and contributes to the academic research of knowledge management in the context of enterprise systems assimilation.