Anxiety difficulties and disorders are common in children and youth people with Autism Spectrum Disorders (ASD), but only a few studies have specifically examined informant agreement in non-referred samples. The present study examined informant agreement between 38 Singaporean caregiver-child dyads using the Spence Children's Anxiety Scale Parent Version (SCAS-P) and the SCAS Child self-report (SCAS-C) respectively. The young people with ASD (mean age 12 years 10 months) completed the SCAS-C, while their caregivers completed the SCAS-P, the Scales of Independent Behavior-Revised and the Developmental Behavior Checklist. There was overall moderately good agreement between caregivers and children's reporting of anxiety symptoms. Intra-class correlations were highest in the Separation Anxiety, Generalized Anxiety and Physical Injury subscales. Fourteen of the 38 SCAS items, most of which described overt anxiety symptoms, showed strong or moderate inter-rater agreement. Higher severity of autism symptoms was associated with poorer agreement in the Generalized Anxiety, Panic and Obsessions/Compulsions SCAS subscales. These preliminary findings suggest that the SCAS may be a useful measure for reporting anxiety symptoms in terms of satisfactory agreement between caregivers and young people in non-referred settings. Implications for screening for anxiety in non-referred young people with ASD are also discussed.