Abnormalities of the sex chromosomes (47, XXY, 47 XYY, 45,X/46,XY mosaicism) are frequently associated with Autism Spectrum Disorders (ASD), but the male predisposition to these disorders has not been clearly explained. Previously, the role of the X chromosome was considered important in the ASD mainly because autistic symptoms were detected in genetic syndromes involving X chromosome (fragile X syndrome, Rett syndrome, Klinefelter syndrome). Instead, few studies have analyzed the possible role of the Y chromosome in the ASD. This study explores the role of the Y chromosome in ASD through a systematic literature review about the association between ASD and XYY syndrome and a description of two new cases with this association. The literature review considered studies published in peer-reviewed journals, included in the MEDLINE and PubMed databases, that examined the association between ASD and XYY syndrome. Few studies reported the occurrence of ASD in children with XYY karyotype and the majority of them did not reported a well-defined autism diagnostic category associated with an extra Y chromosome, but several clinical conditions that are generically described as language and social impairment. Conclusion: This study underlines the underestimated role of the Y chromosome in ASD, and we postulate that all the ASD associated with the XYY karyotype may presumably fall within mild degree of ASD as in our cases.