Purpose: The PEDI-CAT (ASD) is used to assess functioning of children and youth on the autism spectrum; however, current psychometric evidence is limited. This study aimed to explore the reliability, validity and acceptability of the PEDI-CAT (ASD) using a large Australian sample. Methods: Caregivers of 134 children and youth on the spectrum participated in clinical assessments involving the administration of the PEDI-CAT (ASD), Vineland-3, PEDI-CAT (Original) and a feedback instrument. The PEDI-CAT (ASD) content was compared to the ICF Core Sets for ASD to summarize areas of functioning assessed and relevance to autism. Results: The PEDI-CAT (ASD) demonstrated good to excellent internal consistency and test-re-test reliability. Parallel forms reliability with the PEDI-CAT (Original) included significant correlations (good to excellent), however, t-tests showed significantly higher Social/Cognitive scores for the ASD version. Convergent validity results demonstrated that most PEDI-CAT (ASD) and Vineland-3 core domains were significantly correlated (poor to good). Content analysis revealed that the PEDI-CAT (ASD) covered less than half of the ICF Core Sets for ASD (mostly Activities and Participation codes). Just over half the codes assigned to the PEDI-CAT (ASD) were represented in the ICF Core Sets for ASD. Feedback on the acceptability of the measure was mixed, but overall was it was considered user-friendly and efficient. Conclusion: The PEDI-CAT (ASD) had adequate psychometric properties and acceptability as a measure of Activities and Participation codes. However, it lacks comprehensiveness and relevance when compared to the ICF Core Sets for ASD and has the potential to overestimate functioning.