How do followers react to their leaders' emotional expressions and how do these reactions influence followers' perceptions of their leaders' effectiveness? This research examines cognitive and emotional reactions to leaders' expressions of positive and negative emotions and demonstrates how these reactions affect perceptions of leadership effectiveness. We show that follower interdependence (dispositional or manipulated) plays an important moderating role in understanding reactions to leaders' emotions. Results of three studies demonstrate that followers not only share their leaders' emotions but also make attributions about the sincerity of their leaders' intentions and these attributions affect their perceptions of their leader's effectiveness. Results also demonstrate that interdependent followers are sensitive to leader emotional valence and react more positively to leader positivity; non-interdependent followers do not differentiate positive from negative emotions in their leader. We discuss the implications of our research for the literature on leadership.