<p>Recently, scholars have shown a growing interest in exploitative leadership, which refers to leaders pursuing their own interests by exploiting followers. While the accumulated evidence demonstrates a wide array of negative consequences of exploitative leadership, we explore why and when leaders are exploitative, thus offering insights into the prevention of exploitative leadership behavior. Drawing on trait activation theory, we propose that leaders with a Machiavellianism trait are more (versus less) likely to exhibit exploitative leadership due to activated (versus decreased) self-serving cognition when they weakly (versus strongly) perceive that they are accountable for their decisions and behaviors at work (i.e., accountability). To test our hypotheses, we collected three waves of survey data from 195 leaders and 587 followers. The results of multilevel analysis show that the interaction of leaders’ Machiavellianism and accountability is related to exploitative leadership via leaders’ self-serving cognition. Specifically, the relationship between leaders’ Machiavellianism and exploitative leadership via leaders’ self-serving cognition is stronger when accountability is lower but is nonsignificant when accountability is higher. The present research provides important theoretical and practical insights into the determinants of exploitative leadership.</p>