Self-confidence is associated with many positive outcomes, and training programs routinely seek to build participants’ self-efficacy. In this article, however, we consider whether self-confidence increases unethical behavior. In a series of studies, we explore the relationship between negotiator self-efficacy—an individual’s confidence in his or her negotiation ability—and the use of deception. We find that individuals high in negotiator self-efficacy are more likely to use deception than individuals low in negotiator self-efficacy. We also find that perceptions of the risk of deception (...) mediate this relationship. By identifying negotiator self-efficacy as an antecedent to unethical behavior, our findings offer important theoretical and empirical insights into the use of deception, the role of individual differences in ethical decision making, and the broader consequences of self-confidence in business and society. (shrink)