This study examined the nature and correlates of hoarding among youth with autism spectrum disorders (ASD). Forty children with ASD and a comorbid anxiety disorder were administered a battery of clinician-administered measures assessing presence of psychiatric disorders and anxiety severity. Parents completed questionnaires related to child hoarding behaviors, social responsiveness, internalizing and externalizing behaviors, and functional impairment. We examined the impact of hoarding behaviors on treatment response in a subsample of twenty-six youth who completed a course of personalized cognitive-behavioral therapy targeting anxiety symptoms. Hoarding symptoms were common and occurred in a clinically significant manner in approximately 25% of cases. Overall hoarding severity was associated with increased internalizing and anxiety/depressive symptoms, externalizing behavior, and attention problems. Discarding items was associated with internalizing and anxious/depressive symptoms, but acquisition was not. Hoarding decreased following cognitive-behavioral therapy but did not differ between treatment responders and non-responders. These data are among the first to examine hoarding among youth with ASD; implications of study findings and future directions are highlighted.