RAS p21 activator 3 gene is a member of the Ras GAP1 family of GTPase-activating proteins. DNA methylation is the most well-known epigenetic mechanism. Abnormality on RAS proteins which are regulated by RASA3 may play a critical role in Autism. Autism is a complex of neurodevelopmental disorders. Defining the regulators of RASA3 is important to understand its role in Autism. This study included 19 Saudi autistic children and their healthy siblings. Blood was used to analyze the differential expression of RASA3 and its transcriptional factor Specificity protein 1. qRT-PCR and MethyLight assay was used to measure CpG sites methylation on TFBs in the promoter of RASA3 to investigate the association between methylation level and TF in the regulation of RASA3 expression. Results showed differential expression patterns for both RASA3 and Sp1 genes with a significant positive correlation between them. There was no difference in RASA3 methylation level in such binding sites of the target region in the promoter of RASA3 in autistic and healthy samples. The data suggested that the Sp1 could play a critical role in the regulation of RASA3 expression while DNA methylation does not. However, it remains an open question whether the dysregulation of RASA3 by methylation in other regions may be implicated in the development of ASD.