The present invention relates generally to a method for diagnosing autism spectrum disorder (ASD) in a biological sample obtained from a subject comprising the steps of: i) extracting the miRNAs from the biological sample, ii) determining the level of at least one miRNA selected from miR-19a-3p, miR-361-5p, miR-3613-3p, miR-150-5p, miR-126-3p, and/or miR-499a-5p in the nucleic acid extraction; iii) comparing the level measured at step ii) with its predetermined reference value, and iv) concluding that the subject suffers from ASD when the level of at least one miR-19a-3p, miR-361-5p, miR-3613-3p, miR-150-5p, miR-126-3p, and/or miR-499a-5p is lower than its predetermined reference value or concluding that the subject does not suffer from ASD when the level of at least one miR-19a-3p, miR-361-5p, miR-3613-3p, miR-150-5p, miR-126-3p, and/or miR-499a-5p is the same value as its predetermined reference value. rnInventors report a characteristic miRNA profile of expression of six miRNA genes detected by quantitative qRT-PCR analysis in human patients and further evidenced in two established animal models of the disease. MicroRNAs miR-19a-3p, miR-361-5p, miR-3613-3p, miR-150-5p, miR-126-3p, and miR-499a-5p were found to be expressed at low to very low levels in the serum of 45 human patients with autism.