Mergers between retailers are common in business activities and involve the O2O (online to offline) supply chain decision-making model under two scenarios: the manufacturer provides one product (both new and remanufactured) to two retailers, respectively, in a premerger scenario (Model P); the manufacturer wholesales the product but only to a stronger dual-line retailer in a merger scenario (Model M). The results show that the quantity of new products in Model P is lower than that in Model M, while the quantity of remanufactured products is higher than that in Model M. When compared to Model P, Model M improved the dual-line retailers’ financial performance while cutting into manufacturer and industry profits.