<p>Although follower helping behavior has been widely studied, knowledge about how such behavior promotes negative behavior from third-party observers is still limited. Drawing upon social cognitive theory, we conceptualize leaders as the third-party observers of follower helping behavior, and develop and test a theoretical model of how and when follower helping behavior affects leader exploitation behavior. Through an experiment and a multi-wave survey study, we found that follower helping behavior was positively related to leader perceptions of followers’ willingness to self-sacrifice, which in turn increased leader exploitation behavior. Furthermore, we found that leader bottom-line mentality moderated the indirect effect between follower helping behavior and leader exploitation behavior via leader perceptions of followers’ willingness to self-sacrifice, such that the positive indirect effect was stronger for leaders with high (rather than low) bottom-line mentality. Taken together, our findings present a novel framework for understanding how follower helping behavior can give rise to detrimental leader behavior, thereby inspiring the ongoing interest of scholars and practitioners in helping and leadership research.</p>