Recent theory and evidence support an integrated affective-cognitive model of adolescent depressive symptoms in which temperament predicts the use of maladaptive cognitive emotion regulation (ER) strategies which, in turn, predict depressive symptoms. We concurrently and prospectively investigated whether two cognitive ER strategies (dampening and brooding) mediated the effect of trait positive and negative affect on adolescent depressive symptoms. Young adolescents (11-14 years old) completed questionnaires at baseline (N = 150) and at a 4-month follow-up (N = 126). Findings indicate brooding mediated the relationship between both positive and negative affect and depressive symptoms, both cross-sectionally and prospectively. Dampening yielded inconsistent results. This suggests brooding may be a unique mechanism from trait affect to depressive symptoms in late childhood to early adolescence.