This study examined informant discrepancies for parent and teacher adaptive behavior ratings of 103 children, ages 6–12 years, with ASD (without intellectual disability). Scores on the Adaptive Behavior Assessment System, third edition (Harrison and Oakland, Western Psychological Services, Los Angeles, 2015) General Adaptive Composite (GAC) and practical, social, and conceptual domains were examined for mean differences, level of agreement, and moderators of difference scores between informant groups. Teacher scores were significantly higher (indicating better functioning) than parents for the GAC and practical domain. Parent and teacher scores were moderately correlated and Bland–Altman plots and regression analyses revealed no systematic differences in parent–teacher agreement across the range of scores. None of the tested variables moderated the parent–teacher difference scores. Implications for clinical practice are discussed.