Buyers often make supplier selection decisions under conditions of uncertainty. While the analytical aspects of supplier selection are well developed, the psychological aspects are less so. This paper uses literature from supply chain management and behavioral decision theory to propose the following: While attributes of a purchase category (i.e., category difficulty, category importance, and contingent pay) influence risk perceptions, cognitive processes exist that additionally influence risk perceptions and affect a supply manager's choice. We conducted a supplier selection behavioral experiment with practicing managers to test the model's hypotheses. When the context involves an important or difficult sourcing category, higher risk perceptions exist that increase preferences for a supplier with more certain outcomes, even when that decision has a lower expected payoff. However, the presence of contingent pay decreases risk perceptions through higher perceived supplier control. Also, we find that a manager's risk propensity increases preferences for a supplier with less certain outcomes regardless of perceived risk. Our model and results provide a theoretical framework for further study into the cognitive aspects of supplier selection behavior and provides insight into decisional biases that practicing supply chain managers may be subject to.