Purpose: Interfirm knowledge sharing has been well recognized to activate the performance and competitiveness improvement of the firms. Previous research has discussed the impacts of current suppliers on buyer–supplier knowledge sharing, but does not explain how this influence occurs. This study aims to disclose the mechanism by which both current and competing suppliers impact buyer–supplier knowledge sharing in buyers’ new product development activities. Methodology/approach: This study proposed a conceptual model based on relational exchange theory and developed eight hypotheses. Questionnaire survey was used to collect empirical data from R&D staff of Taiwanese electronics firms. This study distributed 1,475 questionnaires and received 246 eligible questionnaires. Structural equation modeling was used to test and verify appropriateness of the proposed model. Findings: The findings show that current supplier asset specificity positively and directly influences buyer–supplier knowledge sharing in new product development. The current supplier asset specificity also has indirect positive influence on buyer–supplier knowledge sharing in new product development via the mediating effects of buyer trust, satisfaction, and commitment. However, the attractiveness of alternative suppliers only indirectly and negatively affects buyer–supplier knowledge sharing via the mediating effects of buyer trust, satisfaction, and commitment. Research limitations/implications: This study surveyed the firms in Taiwanese electronics industry. Nevertheless, new product development activities are executed by electronics firms in numerous countries and firms in various industries. For validating the generalization of this study’s results, future research can investigate firms in other industries and countries to verify the proposed model and hypotheses. Practical implications: Current suppliers’ asset specificity is found to exert more influence on buyer–supplier knowledge sharing than alternative attractiveness. The findings imply that current suppliers should focus on investing specific assets for buyers other than stress the attractiveness and threat of competing suppliers. Originality/value/contribution: This study initiates to approach the antecedents and influence mechanism of current buyer–supplier knowledge sharing via both perspectives of current and competing suppliers.