Emotional displays of leaders convey social information to followers that can help bolster their motivation and understanding of the situation, thereby facilitating team performance. An implicit assumption in previous theorizing and research using this social-functional approach to leader emotions has been that leaders’ emotional expressions logically follow from the situation for followers and thus help followers who observe these expressions to better understand the situation. However, leader's emotional expressions are not always predictable to followers. We extend the social-functional approach by investigating what happens when leader emotional displays are perceived as unpredictable by followers. We propose that leader emotional unpredictability sparks uncertainty among followers about how the leader allocates ranks and resources within the team, which triggers intra-team power struggles. Such power struggles—intra-team conflicts over resources among followers—in turn undermine team performance. Using a multi-method approach, we find support for our model in three studies, including two laboratory experiments and a field study of 246 retail teams. The findings inform our understanding of how leaders’ emotional displays influence team performance, extending the social-functional approach to emotion by illuminating how the perceived unpredictability of leaders’ emotional expressions can be dysfunctional for teams.