Background: Autism spectrum disorder (ASD) is a set of neurodevelopmental disorders which affects communication, cognition and behavior. It is termed as a “spectrum" disorder because of the wide variation in the type and severity of symptoms people experience. Symptoms generally appear in the first two years of life. Aim of the work: To summarize evidence on the prevalence, etiology, pathogenesis, diagnosis and treatment of ASD and role of experimental animals. Observations: Pathogenesis of ASD represents an area of great uncertainty and yet the many postulated mechanisms are poorly understood. Several theories to regarding ASD pathogenesis exist; neural connectivity, neural migration, and excitatory-inhibitory neural activity. Immune disturbances and glial cell dysfunction were also presumed to play a role. There is still no direct and definite mechanism explaining the pathogenesis of ASD. Diagnosis of ASD can be difficult but it is crucial to ensure receiving support and help as soon as possible. ASDs are generally not “curable," but the main goals of treatment are to lessen associated deficits and family distress, and to increase quality of life and functional independence. Medical, behavioral, or complementary and alternative lines of treatment are employed. Animal models of autism are being developed to meet the urging need for investigating the underlying causes of ASD and to find the proper medication to help treat the condition or control its symptoms. Conclusion: The exact cause of autism spectrum disorder is so far unknown. Further work is needed to broaden the horizons on the understanding of ASD.