The role of key supplier relationships and their link with purchasing performance are poorly recognized in current business-to-business marketing literature. Given the predominance of collaborative supply chain relationships, purchasing must be considered to be providing value, thereby implying its effective nature. This study introduces a conceptual model of the relationship between supply chain orientation (SCO) and key supplier relationship management (KSRM) with organizational buying effectiveness (OBE) as a measure of effective purchasing behavior. To extend the model's nomological network, we link OBE with firm profitability. Wefind that SCO and KSRMhave a strong positive influence on OBE. Furthermore, KSRMis demonstrated to be a significant mediator in the SCO–OBE relationship. Finally, OBE significantly and positively influences firm profitability, suggesting that it adequately addresses the aspects of effective purchasing behavior.We also discuss theoretical and managerial implications as well as future research directions in light of the limitations of this study