In this paper, we investigate the notion of organizational ambidexterity in using interorganizational system (IOS) in supply chain context. IOS ambidexterity is defined as a firm's capability of simultaneously pursuing exploratory and exploitative use of IOS. In order to understand the implication of IOS ambidexterity in IT resource-constrained firms, this paper draws on theories in resource-based view and organizational ambidexterity literature. Based on data collected from 375 firms and PLS analysis, this work empirically confirms that a firm capable of using IOS in a more ambidextrous way tends to experience greater performance improvement and that different types of IT resources exhibit differing influence patterns on IOS ambidexterity and performance. An additional analysis is performed to understand the moderating role of IT resources in the IOS ambidexterity-performance linkage.