Aims: The present study aims to screen autism spectrum disorder in children attending pediatric clinic. Methods: This descriptive cross-sectional study was carried out on 1500 children aged 1.5 to 4 years old in pediatric clinic in Khorramabad. After recording the demographic data, the Modified Checklist for Autism in Toddlers screening test was performed in this study Results: Out of 1500 participants, 704 (46.9%) were boys and 796 (53.1%) were girls. The age group of 18-36 months had the highest screening (74%). 23 (1.5%) of the participants had diagnostic and statistical criteria for Autism Spectrum disorders. Conclusion: The screening shows that, 23 in 1500 had autism in this study, which shows its high value in the country. Therefore, further assessments are recommended on the causes of this high number with larger sample sizes over a longer period of time, along with investigation of the relationship between the factors of autism.