© 2020 Elsevier Ltd Background: Cognitive behavior therapy (CBT) for youth with autism spectrum disorder (ASD) and anxiety has a strong evidence base. However, few studies have examined clinicians’ sustained use of CBT programs after training efforts have ended. The present study is a follow-up to a clinical trial that examined the implementation and treatment outcomes in response to a group CBT program for youth with ASD and co-occurring anxiety (i.e., Facing Your Fears; FYF). This study uses a mixed-methods approach to understand: 1) the percentage of clinicians who continue to use FYF at least four years after being trained in the program (i.e., sustainment); 2) adaptations that have been made to FYF in order to sustain its fit within clinical settings; and 3) factors that influence clinicians’ sustained use of FYF. Method: Thirty of 34 clinicians who were initially trained to use FYF responded to a mixed-methods survey asking about their sustained use of the program, adaptations made to FYF, attitudes towards FYF, and perceived barriers to continued FYF use. Results: Results demonstrated that a majority of clinicians reported that they continue to use the FYF program. Clinicians described that they continue to use FYF due to their perceptions of the program's effectiveness, ease of use, and compatibility, but also made a variety of adaptations to FYF. Conclusion: Results from the present study help to better understand factors impacting the sustained use of CBT for youth with ASD. They also highlight the importance of proactive efforts within clinical training to plan for intervention adaptation and to consider factors likely to impact program sustainment.