Objective Emotion reactivity and difficulties in expressing emotions have been implicated in risk for suicidal behavior. This study examined comfort in expressing emotions (positive vs. negative) and depressive symptoms as mediators of the prospective relation between emotion reactivity and suicidal ideation. Design Emerging adults (N = 143; 72% female; 28% White) completed measures of emotion reactivity, comfort expressing emotions, and suicidal ideation at baseline and of depressive symptoms and suicidal ideation 12 months later. Results Emotion reactivity predicted suicidal ideation at follow‐up through depressive symptoms. Difficulty expressing love–but not happiness, sadness, and anger–partially mediated the relationship between emotion reactivity and suicidal ideation at follow‐up before but not after adjusting for baseline ideation. Conclusion The relation between high emotion reactivity and suicidal ideation may be explained by discomfort in the expression of positive emotions and by depressive symptoms. Promotion of comfort in positive emotion expression may reduce vulnerability to suicidal ideation.