Objective: Accommodation, or the ways in which families modify their routines and expectations in response to a child's anxiety, is common and interferes with anxiety treatment outcomes. However, little research has examined family accommodation among youth with autism spectrum disorder and anxiety. The current study aimed to (a) identify pre-treatment correlates of accommodation, (b) examine changes in accommodation after treatment, and (c) assess relationships between accommodation and post-treatment anxiety severity.Method: The sample consisted of 167 youth (mean age = 9.90 years; 79.6% male; 18% Latinx) with clinically significant anxiety and a diagnosis of autism spectrum disorder who were enrolled in a randomized clinical trial comparing two cognitive behavioral therapy interventions for anxiety and treatment-as-usual. Participants were evaluated for symptom severity and family accommodation at pre- and post-treatment.Results: Results indicated that clinician-rated anxiety severity and parent-rated externalizing behaviors and autism spectrum disorder severity significantly predicted pre-treatment accommodation. Accommodation significantly decreased from pre- to post-treatment and non-responders showed significantly higher accommodation at post-treatment compared to responders. Finally, youth with higher pre-treatment accommodation had higher post-treatment anxiety.Conclusions: Findings indicate that accommodation for anxiety is common among youth with autism spectrum disorder and anxiety. Furthermore, accommodation is implicated in treatment outcomes and should be targeted in treatment for youth with autism spectrum disorder and anxiety.