<p>This study investigates the coexistence of multiple channel-related phenomena—intershowrooming, intrashowrooming, and webrooming—within a multi-channel supply chain. A Stackelberg game model, combined with numerical simulations, is developed to explore how these overlapping effects shape the pricing and sales effort decisions of supply chain members. The results reveal that: (1) Intershowrooming temporarily enhances the retailer's profitability by concentrating online demand, but gradually erodes the pricing power of the offline channel. When the retailer’s online market share is relatively low, a “high-offline-price, low-online-price” strategy is more effective, and the applicability of this strategy expands as the intensity of webrooming increases. (2) When both showrooming and webrooming effects are at moderate levels, differentiated pricing and sales efforts across channels generate synergistic gains. Sales efforts in both offline and online channels increase product prices; however, when these effects become intense, a “synergy failure threshold” may emerge, at which point the marginal return to additional effort becomes negative. (3) The effects of showrooming and webrooming are asymmetric. webrooming enhances the retailer's profitability through centralized consumer redirection, whereas showrooming dilutes demand and diminishes the return on sales investment. This study refines showrooming into internal and external pathways, and explores optimal decision-making under the overlapping presence of multiple channel phenomena, offering managerial insights into pricing and sales effort strategies to mitigate channel conflict.</p>