Many theories of moral behavior assume that unethical behavior triggers negative affect. In this article, we challenge this assumption and demonstrate that unethical behavior can trigger positive affect, which we term a "cheater's high." Across 6 studies, we find that even though individuals predict they will feel guilty and have increased levels of negative affect after engaging in unethical behavior (Studies 1a and 1b), individuals who cheat on different problem-solving tasks consistently experience more positive affect than those who do not (Studies 2-5). We find that this heightened positive affect does not depend on self-selection (Studies 3 and 4), and it is not due to the accrual of undeserved financial rewards (Study 4). Cheating is associated with feelings of self-satisfaction, and the boost in positive affect from cheating persists even when prospects for self-deception about unethical behavior are reduced (Study 5). Our results have important implications for models of ethical decision making, moral behavior, and self-regulatory theory.