Background: More than 90% of cases of autism spectrum disorders (ASDs) are idiopathic and are multi-factorial inheritant in etiology. Although parental perceptions of ASDs etiologies including genetics have been investigated well in western countries, there is no study regarding Asian parental perspectives on the genetic etiology of ASDs. Objectives: Examine what Thai parents perceived to be the etiology of ASDs with particular focus on the role of genetics, and analyze the correlation between demographics of parents and the perception of genetics as an etiology of ASDs. Methods: Children diagnosed with an ASD at Ramathibodi Hospital were recruited, and 328 questionnaires were mailed to their parents between February 1 and March 31, 2008. Based on 252 answers received, the perception of genetics as an etiology of ASDs was evaluated using univariate and multivariate analysis. Results: Among 252 parents, 44.0% cited genetics, 52% cited other prenatal and perinatal factors such as stress and chemical exposure during pregnancy, 33% cited postnatal factors such as child rearing, child’s viewing of television, and playing computer game as etiologies of ASDs. Parents’ education, positive family history of ASDs, and positive family history of speech delay were all significantly associated with the perception of genetics as an etiology of ASDs. Conclusions: Less than half of Thai parents cited genetics as an etiology of ASDs. This finding alerts medical professionals to spend more time and effort to educate and counsel parents.