Deficits in emotional clarity, the understanding and awareness of one’s own emotions and the ability to label them appropriately, are associated with increased depressive symptoms. Surprisingly, few studies have examined factors associated with reduction in emotional clarity for adolescents, such as depressed mood and ruminative response styles. The present study examined rumination as a potential mediator of the relationship between depressive symptoms and changes in emotional clarity, focusing on sex differences. Participants included 223 adolescents (51.60% female, Mean age = 12.39). Controlling for baseline levels of emotional clarity, initial depressive symptoms predicted decreases in emotional clarity. Further, rumination prospectively mediated the relationship between baseline depressive symptoms and follow-up emotional clarity for girls, but not boys. Findings suggest that depressive symptoms may increase girls’ tendencies to engage in repetitive, negative thinking, which may reduce the ability to understand and label emotions, a potentially cyclical process that confers vulnerability to future depression.