IOS integration (IOSI) is becoming a competitive necessity in an industrial environment that emphasizes competition between supply chains. In the supply chain, dominant firms often try to exert their power to influence their dependent firms to implement IOSI. Misunderstanding about how power operates will impede firms for developing IOSI. Based on the circuits of power framework and the concept of obligatory passage point (OPP), this study identifies three factors that should mediate the effect of power on the implementation of IOSI, including competitive necessity, expected benefits, and firm readiness. We accordingly develop a theoretical model with nine hypotheses. Based on a sample of 135 manufacturing firms, seven out of the nine hypotheses receive empirical support using PLS. The findings show that the flows of exercised power and potential power into IOSI indeed circulate through those mediators. The theoretical and practical implications of the results contribute a better understanding of how power operates in developing IOSI.