Evaluated the psychometric properties of a newly created measure of cognitive vulnerability to depression for use with adolescents. Previous measures have shown poor internal consistency reliability and have not completely assessed all hypothesized components of cognitive vulnerability. High school students completed questionnaires assessing cognitive vulnerability to depression, negative life events, depressive symptoms, and general internalizing and externalizing symptoms. The Adolescent Cognitive Style Questionnaire (ACSQ) demonstrated excellent internal consistency reliability and good test-retest reliability. Confirmatory factor analysis showed there were 3 latent factors to the ACSQ. Construct validity was supported by significant correlations with another attributional style questionnaire, as well as with depressive and internalizing symptoms. The interaction of ACSQ with negative events significantly predicted concurrent depressive and internalizing symptoms but not externalizing problems. Last, cognitive vulnerability mediated the gender difference in depressive symptoms. Overall, results suggest that the ACSQ is a highly reliable and valid measure of cognitive vulnerability to depression in adolescence.