We present a theoretical rationale and supporting studies revealing how unethical leader behavior fosters an unethical climate within workgroups that increases member turnover intentions and malfeasance. Drawing on the attraction–selection–attrition model of organizational behavior, we propose a selective attrition effect whereby unethical leader behavior results in the retention of group members who are more comfortable with dishonesty and, consequently, more likely to engage in unethical behavior toward their group. In two experiments, exposure to unethical leader behavior increased group members’ likelihood (...) of choosing to leave the group. Members who chose to remain in a group with an unethical leader were more likely than those who chose to leave to cheat their group in a subsequent task. A two time-period survey replicated these findings and identified psychological distress as the mechanism driving group members’ turnover intentions. This research extends our understanding of the complex relationships between unethical leadership and follower turnover intentions, psychological distress, and malfeasance. We contribute to the behavioral ethics literature by identifying a previously underappreciated form of selective attrition that produces internal costs to groups and organizations, independent of reputational consequences and whether the unethicality is publicized. (shrink)