This study extends the existing adult literature on insecure attachment as a predictor of depression and anxiety by examining these pathways in a sample of adolescents. In addition, dysfunctional attitudes and low self-esteem were tested as mediators of the association between insecure attachment and symptoms of depression and anxiety. Youth (N = 350; 6th-10th graders) completed self-report measures of attachment, dysfunctional attitudes, self-esteem, and symptoms of depression and anxiety in a 4-wave prospective study. Results indicate that anxious and avoidant attachment each predicted changes in both depression and anxiety (after controlling for initial symptom levels). The association between anxious attachment, but not avoidant attachment, and later internalizing symptoms was mediated by dysfunctional attitudes and low self-esteem. Effects remained even after controlling for initial co-occurring symptoms. (Contains 2 tables and 2 figures.)