Autism spectrum disorder (ASD) is neurodevelopment disorder, characterized by impairment in social interaction, verbal and non-verbal communication and the presence of restricted and repetitive stereotyped behaviors. The condition manifests within the first 3 years of life and persists till adulthood. At present, the etiology of ASD is largely unknown, but genetic, environmental, immunological, and neurological factors are thought to play a role in the development of ASD. The prevalence of ASD has increased dramatically in the past few decades. According to current estimates from the United States Centers for Disease Control and Prevention (CDC) as many as 1 in 91 children have ASD in USA. Studies from the Middle East on this topic are limited. Autism in Saudi Arabia is slightly higher than reported in the developed countries. Hyperbaric oxygen therapy (HBOT) has been growing in popularity for the treatment of ASD over recent years. However, few studies of its effectiveness have been reported. This article reviews important publications regarding the physiologic and clinical influence of HBO on ASD. Several case series and randomized trials have all proposed that low pressure/ low oxygen concentration hyperbaric treatment can improve the clinical manifestations of autism.