Autism spectrum disorders (ASD) are common neurodevelopmental syndromes affecting 1% of U.S. children. Comorbid anxiety disorders affect 40 to 50% of children with ASD, causing substantial distress and impairment over and above that caused by ASD alone. Although standard practice cognitive-behavioral therapy (CBT) has been established as an efficacious and safe treatment for anxiety disorders among typically developing youth, its utility in comorbid cases with ASD remains unknown. To date, no studies have experimentally compared standard practice CBT to a cognitive-behavioral intervention that has been personalized for children with a comorbid presentation of anxiety and ASD. Accordingly, we are proposing a randomized controlled trial to be conducted at three treatment sites to evaluate the efficacy of personalized CBT for anxiety in ASD (Behavioral Intervention for Anxiety in Children with Autism: BIACA) relative to standard practice CBT for anxiety (Coping Cat program). Furthermore, this study will employ a waitlist control group to assess the efficacy of each CBT arm relative to the absence of treatment (i.e., a Waitlist control arm). The proposed research will: (1) examine the efficacy of BIACA relative to Coping Cat, which represents standard practice treatment, and the efficacy of both these treatments relative to a waitlist control group, (2) evaluate the maintenance of treatment gains, (3) examine the impact of personalized intervention on functional outcomes. A total of 201youth across 3 study locations (ages 8-13 years) with ASD and co-occurring anxiety will be randomly assigned to one of the three conditions. The three recruitment sites for this study are University of California, Los Angeles, the University of South Florida (USF), and Temple University. Considering the rising number of children diagnosed with ASD together with the frequency and severity of comorbid anxiety, the proposed work is tailored to the unique needs of youth with ASD and will provide a timely contribution to public health efforts.