AbstractThis paper considers an outsourced supply chain comprising a contract manufacturer (CM), an original equipment manufacturer (OEM) and an online platform. In addition to providing contract manufacturing services to the OEM, the CM enters the market using the customer‐to‐manufacturer (C2M) strategy. Two baseline models and four encroachment models with different selling modes are modeled to explore the interaction among CM encroachment, selling modes and the C2M strategy. We find that the CM will always encroach if brand substitution is sufficiently high. However, the CM will still encroach despite brand substitution being low if the platform charges the OEM a high commission rate in Scenario PR. The results also show that the CM may increase or decrease the wholesale price charged to the OEM according to his dependence on the OEM channel and direct channel. Finally, we find that after CM encroachment, the OEM is worse off, while the platform may be better or worse off. The profits of the CM, OEM, and platform decrease if customers are more concerned about production flexibility. Our work provides guidance for CM encroachment from the perspective of channel choice and product strategy and offers managerial insights into C2M practice.