Examine the concurrent validity of specific Anxiety Disorders Section of the Anxiety Disorder Interview Schedule for DSM-IV-Autism Spectrum Addendum (ADIS-ASA)-Parent Interview in a sample of 167 autistic youth who met diagnostic criteria for an anxiety-related disorder (Mage = 9.91; 78.4% male; 82% non-Hispanic; 77.67% White). Concurrent validity of Diagnostic and Statistical Manual (DSM)-defined ADIS-ASA anxiety disorder diagnostic caseness was examined via relations with (a) parent-reported dimensions of youth anxiety symptomology and (b) dimensional measures of youth anxiety-related functional impairment, respectively, using logistic regression models and point-biserial correlations. Significant relations were found between separation anxiety disorder and social anxiety disorder (but not generalized anxiety disorder nor obsessive-compulsive disorder) caseness, respectively, and theoretically consistent facets of dimensional youth anxiety symptomology. Relations between ADIS-ASA diagnostic caseness and youth functional impairment-related variables revealed that only separation anxiety disorder demonstrated robust evidence of convergent validity. Despite mixed findings concerning relations between ADIS-ASA anxiety disorder diagnostic caseness and dimensional measures of anxiety severity and anxiety-related impairment, the present findings provide further support for the status of the ADIS-ASA as a gold standard for assessment of anxiety in autistic youth. This work also highlights the importance of continuing to improve precision in measurement of anxiety symptomology in autistic youth, with implications for clinical assessment.