Autism spectrum disorder (ASD) is a large group of neurodevelopmental conditions that share common characteristics such as social and language impairment and repetitive and stereotypic behaviors. It is reported that ASD is on increase in recent years reaching ratios up to 1 in 68 children. The disease is seen four times more frequently in males than females. ASD is heritable with complex inheritance and genetic heterogeneity, and frequently coexists with other diseases such as intellectual disability, seizure disorders, and fragile-x. Recent advances in genomic technologies have led to a greater understanding of genetic mechanisms in ASD, discovery of novel genetic loci and risk factors, as well as submicroscopic chromosomal changes also known as copy number variations (CNVs). Here we review recent developments in the genetics field and hereditary and sporadic CNVs leading to ASD.