Background: In Saudi Arabia, too few studies are published regarding the dental health habits of children with Autistic Spectrum Disorders (ASD). Aim: The aim of this study was to evaluate their parents’ dental knowledge; and the oral hygiene practices of a group of autistic children. Subjects and Methods: This is a cross-sectional study targeting parents of autistic children enrolled in three different rehabilitation centers in Riyadh. A total of 450 selfadministered questionnaires formulated in simple Arabic were distributed to parents of children diagnosed with autism or any form of ASD. The questionnaires consisted of demographic questions and dental-related questions, such as the sources of dental knowledge, causes of dental problems, and opinion about the proper time of first dental visits. Results: The majority of the participating parents didn’t receive any dental knowledge from dental personnel. More than 60% of the parents reported that their children were unable to brush their teeth by themselves. In addition, the results showed that 90% of the children used toothbrushes and pastes, and only 34% of them brushed their teeth once per day, Furthermore, more than half of the mothers reported that they helped their children during tooth brushing. The parents did not have proper knowledge about the timing of children‘s first dental visit. Conclusions: Based on the results, it can be concluded that there is lack in dental knowledge within the participating group of parents in this study. Dental professionals should increase their efforts to educate their patients about dental knowledge.