This study tested the role of emotion in structured ideation, a process in which newly generated ideas and insights closely follow previously generated ideas and insights. Emotions can be differentiated on a number of underlying dimensions, including uncertainty, and uncertainty can influence information processing. On these grounds, we proposed and tested the idea that (1) emotions that associate with appraisals of uncertainty (fear, sadness) lead to more structured ideation than emotions that associate with appraisals of certainty (happiness, anger) and that (2) appraisals of uncertainty drive this effect. Findings of four experiments on idea generation in which (un)certainty was primed (Study 1) and emotions were induced through self-generated imagery (Study 2-4) supported these predictions.