Background: Autism Spectrum Disorder (ASD) is a specific developmental disability characterized by social and communication impairments, as well as by restricted interests and repetitive behaviors. Autism is become increasing and there is no enough knowledge about it in our society, therefore it is important to to shed a light on such issue. The aim of this study was to evaluate the effect of training program on improving mothers` knowledge about autism. Design: A quasi-experimental study design was carried out. S etting: Speech and Hearing clinic at AL Ahrar Hospital, College of Education of Disability and Rehabilitation at Zagazig University, Moasaset Ramze for Special Needs at Zagazig city. Sample: A convenience sample composed of 50 mothers and their autistic children who have been diagnosed with autism. Tools: Two tools were used to collect the study data: I) A structured interview questionnaire. II) Mothers` knowledge regarding autism structured interview questionnaire. Results: The study results revealed highly statistically significant improvement in mothers` knowledge regarding autism including definition, causes, sign ans symptoms, treatment throughout the study phases pre and post the intervention (P<0.001). Conclusion: The training program is effective in improving mothers` knowledge regarding autism. Recommendation: Orientation of the mothers of autistic children about community resources, care setting and recent information. It is also recommended that future studies with more focus on knowledge about autism.