The study aimed to standardize the Arabic version (translated by the researcher) of the of the Adaptive Behavior Assessment System (ABAS-3) teachers' form identify the psychometric properties and the norms for Omani Students with mild and moderate intellectual disabilities. The sample consisted of (410) male and female students from Al Fikriya School in Muscat and from mainstream schools in the governorates of Muscat, Al Batinah, Al Sharqiya, Al Dakhilia; and Al Wusta. The descriptive method was used in the study and the researcher used appropriate statistical techniques to answer the research questions. The findings of the psychometric properties illustrated the scale suitability to the Omani environment and thus its applicability to be used to diagnose intellectual disabilities cases. Three methods were used to identify the scale validity: face validity, discriminatory validity and concurrent validity. Face validity showed the appropriateness of the scale items to the Omani context. While the discriminatory validity results showed the ability of the scale to discriminate between normal and intellectual disable students. Furthermore, the calculation of the concurrent validity revealed statistically significant results with the correlation coefficient of (0.807). Inter-rater reliability, internal consistency, and test-retest were used to calculate the reliability of the scale. The correlation coefficient between teacher's grades and parent's grades was (0.966); internal consistency of Cronbach's Alpha was (0.992); while test-retest produced the correlation coefficient of (0.969), these results indicated that the scale is highly reliable. Moreover, the means differences analyses using One Way ANOVA revealed significant differences among the age group of the sample. Thus the norms for the sample of the study were obtained using percentile ranks based on the age group. The study ended by some suggestions and recommendations based on the researcher's findings.