Background: The Social Communication Questionnaire-Lifetime (SCQ-L) is a parent report form commonly used to screen for autism spectrum disorder (ASD) symptomology. Further psychometric validation in outpatient settings is essential given the need to prioritize time- and cost-efficient measures. This archival review study examined the internal consistency, construct validity, and predictive validity of the SCQ-L. Method: Participants were the parents of 76 youth aged 4-12 years who presented with developmental concerns at an outpatient ASD clinic (33 diagnosed with ASD and 43 not diagnosed with ASD). Results: Results suggested good internal consistency for the SCQ-L total score and SCQ-L Reciprocal Social Interaction subscale, but questionable internal consistency for the SCQ-L Communication and Restricted, Repetitive, Stereotyped Behavior subscales. There was evidence of construct validity for the SCQ-L total score and subscale scores with other measures of social and adaptive functioning, although the relationships between the SCQ-L scores and ASD severity using the Childhood Autism Rating Scale, 2nd edition-High Functioning Form (CARS2-HF) and daily living skills and the relationship between the SCQ-L Communication subscale and Vineland Adaptive Behavior Scale- Communication subscale (VABS-Communication) were weaker than expected. A cutoff of ≥15 for differentiating youth with ASD from those without ASD was ideal for the sample studied. At this cut-off sensitivity was 0.70 and specificity was 0.67. Conclusions: Overall, this study provides further psychometric support for the use of the SCQ-L and clarifies the appropriate cut-off score that will optimize sensitivity and specificity to identify youth with and without ASD in an outpatient setting, where the use of the SCQ is commonly utilized. ; 8 page(s)