Prior research on leader self‐sacrifice mainly demonstrates its positive role, while less attention has been paid to its potential negative consequences in the workplace. Based on social exchange theory, this study examines how and when leader self‐sacrifice may lead to employees' unethical pro‐organizational behavior (UPB). We tested our hypotheses with three‐wave data gathered from 570 employees. Results showed that leader self‐sacrifice indirectly promoted UPB via leader–member exchange (LMX). Moreover, employees' desire to see themselves in a positive light (i.e., self‐enhancement motives) moderated this indirect relationship, such that the indirect effect was less salient when employees had higher self‐enhancement motives. We discuss this study's implications for the research on leader self‐sacrifice as well as those for practitioners seeking to avoid the potential dangers of positive leadership behavior.