Leaders strive to encourage helping behaviors among employees, as it positively affects both organizational and team effectiveness. However, the manner in which a leader influences others can unintentionally limit this desired behavior. Drawing on social learning theory, we contend that a leader's tendency to influence others via dominance could decrease employees' interpersonal helping. Dominant leaders, who influence others by being assertive and competitive, shape their subordinates' cognitive schema of success based on zero-sum thinking. Employees with a zero-sum mindset are more likely to believe that they can only make progress at the expense of others. We further propose that this zero-sum mindset results in less interpersonal helping among subordinates. We test our hypotheses by employing different operationalizations of our key variables in eight studies of which four are reported in the manuscript and another four in Supplemental Information across a combined sample of 147,780 observations. These studies include a large archival study, experiments with both laboratory and online samples, and a time-lagged field study with employees from 50 different teams. Overall, this research highlights the unintended consequences that dominant leaders have on their followers' helping behavior by increasing their zero-sum mindset. (PsycInfo Database Record (c) 2022 APA, all rights reserved).