Introverts are less likely to emerge as leaders than extraverts, however the existing literature provides little explanation as to why. To investigate the potential cause of this trait-based difference in emergent leadership, we measured trait extraversion in a sample of 184 business students and studied their leadership-related behavior in an unstructured group task. We drew from a model of forecasted affect to hypothesize that introverts would be less likely to emerge as leaders based on their belief that engaging in the necessary extraverted behavior would be unpleasant/unenjoyable (i.e. they would forecast higher levels of negative affect compared to extraverts). Consistent with this, we found that introverts were less likely to emerge as leaders, and that forecasted negative affect fully accounted for the relationship between extraversion and peer-rated emergent leadership. We therefore argue that introverts fail to emerge as leaders as often as extraverts because they engage in higher levels of forecasted negative affect and that these forecasts impede their emergent leadership potential.