The Autism Spectrum Disorder Observation for Children (ASD-OC) is a 45-item observation scale used to assess autistic symptomatology. The reliability of this measure has been established in previous research; therefore, the purpose of this study is to evaluate its validity among a sample of children (1-15 years). The large correlation between the ASD-OC and Childhood Autism Rating Scale (CARS) total scores was significant (r = 0.83), establishing convergent validity for the ASD-OC. To determine divergent validity, the correlation between the ASD-OC total score and the Vineland Adaptive Behavior Scale, Second Edition (VABS-II) Daily Living Skills domain score was analyzed. Although this negative correlation was significant (r =?-0.43), autistic symptom severity has previously been shown to adversely affect daily living skills. Finally, diagnostic groups (i.e., ASD, atypically developing, typically developing) were compared on ASD-OC total scores to establish criterion validity. The ASD group demonstrated significantly higher scores, indicating greater impairment than both the atypically and typically developing groups. ASD-OC scores were also examined by age group (i.e., < 36 months; = 36 months). The implications of these results, as well as directions for future research, are discussed.