This study evaluated the effectiveness of a school-based Cognitive Behavioural Therapy (CBT) on symptoms of anxiety, social worry and social responsiveness, and indices of attentional control and attentional biases to threat in adolescents diagnosed with Autism Spectrum Disorder. Thirty-five young people (11-14 years; IQ > 70) with ASD and elevated teacher or parent reported anxiety were randomly assigned to 6 sessions of the Exploring Feelings CBT intervention (Attwood in Exploring feelings (anxiety). Future Horizons, Arlington, 2004) (n = 18) or a wait-list control group (n = 17). The intervention (compared to the wait-list control) group showed positive change for parent, teacher and self-reported anxiety symptoms, and more marginal effects of increased teacher-reported social responsiveness. The discussion highlights the potential value and limitations of school-based CBT for young people with ASD.