Objectives: The present study aims to develop and evaluate the psychometric properties of the Persian version of Behavior Assessment System for Children, 3rd edition (BASC-3) in children with mild intellectual disabilities and normal children. Methods: This is a cross-sectional study conducted in 2017 on 438 girls and boys with mild intellectual disabilities and normal children aged 12-18 years who were selected using a cluster sampling method. The data collection tool was the Persian BASC-3 and its Parent Rating Scale (PRS-A) and Teacher Rating Scale (TRS-A). Data analysis was performed in SPSS v. 24 using descriptive and inferential statistics. Results: According to the results obtained from factor analysis, assessing correlation of subscale scores with total score, test-retest reliability, and Cronbach’s alpha showed that the Persian BASC-3 and its PRS-A and TRS-A forms had acceptable validity and reliability. Conclusion: The Persian BASC-3 and its parent and teachers forms have good psychometric properties and can be used to evaluate the behavioral and adaptive problems of normal adolescents and children and those with mild intellectual disabilities in Iran.