We test whether leaders' power shapes their reasoning about moral issues and whether such moral reasoning subsequently influences leaders' display of self-interested behavior. We use an incentivized experiment to manipulate two components of leader power: power over more versus fewer followers and power to enforce one's will by having discretion over more versus fewer payout options to allocate between oneself and one's followers. We find that having power over more followers decreased leaders' principled moral reasoning, whereas having higher power to enforce one's will enabled leaders to engage in self-interested behavior. We also find suggestive evidence that power over increases self-interested behavior by ...