This study applies a diagnostic errors framework to identify and classify mistakes that were made in a psychoeducational assessment of a bilingual student who was misidentified as a person with autism. Findings of diagnostic errors were categorized under four domains--faulty knowledge, faulty data gathering, faulty data processing, and faulty verification. This article contributes to the literature by applying a model to understanding the mistakes that could occur during an assessment of special education eligibility. It concludes with considerations for practice and research.