Twin studies provide strong evidence that genetic factors have a major role in the etiology of autism spectrum disorder (ASD) but in most patients the underlying genetic cause of the disease is unknown. Here we used whole-exome sequencing to study genome-wide differences in twins with autism in order to reveal the genetic changes responsible for the etiology of autism. DNA was isolated from peripheral blood samples from six monozygotic twins and one dizygotic twin and analyzed by OneSeq protocol, on an Illumina NextSeq platform. Bioinformatics analyses have revealed 110 disease-related genes, and after further filtering, we have identified 44 single nucleotide polymorphisms (SNPs). Functional network analysis has identified significant associations for 6 different genes, including known ASD candidate genes: FMN2, KCNQ2, NOTCH3, TMRC6A, SHANK3, and SLC6A4. Our results provide an independent evidence for known ASD genes and highlight other genes, which will further improve the understanding of the genetic basis of ASD.