Assessment of anxiety in children with autism spectrum disorder (ASD) most commonly includes parent questionnaires. However, due to the nature of the questions and verbal limitations often present in children with ASD, caregivers may have difficulty completing such measures. Caregivers of 144 children with ASD ages 6 to 12 completed the Child and Adolescent Symptom Inventory-4 ASD Anxiety Scale and rated their level of confidence in responding to each item. Results indicated that parents had a moderate to high level of confidence in rating their children's anxiety symptoms. Parent confidence was not influenced by their child's age, expressive language ability, or intellectual functioning, but was related to their child's anxiety symptom count and ASD severity.