Purpose: Screening and assessment tools for developmental disabilities such as autism may need to be adjusted to particular cultures. The aim of this study was to evaluate the use in Iran of a rating scale for autism commonly used in western society. Method: A Persian translation of the GARS was completed by parents of 658 children: 442 who had been diagnosed with Autism; 112 intellectually disabled and 102 normally developing. The psychometric properties of the subscales were assessed and comparisons made across the three groups. Results: Factor analysis broadly confirmed the three subscales; each of which had high internal consistency. Individuals with autism were clearly distinguished from the other two groups and a cut-off score was identified that maximised the scale’s sensitivity and specificity. Ten items were identified that best discriminated the three groups and these could form the basis for a shorter screening tool as they had good internal reliability and predictive validity. Conclusions: Iranian parents identified items relating to impaired social interaction and repetitive behaviours as more indicative of autism rather than those relating to communication and language. Attuning screening tools to cultural contexts is an important step towards a better understanding of autism internationally.