To assess whether genetic test results identifying the cause of a child's autism, when accompanied by other neurodevelopmental disorders (NDD), including intellectual disability, alter how parents perceive and treat their child. 28 parents of 22 individuals with autism (mean age: 15 years), usually with other NDDs, were interviewed after receiving genetic diagnoses indicating a de novo mutation through the Simons Foundation Powering Autism Research for Knowledge study. Diagnosis of a de novo genetic variant can alter parental perceptions of offspring with autism and other NDDs. Parents often blamed their child less, saw their child as less in control of symptoms, and developed more patience, framing expectations accordingly. Parents had mixed feelings about receiving genetic diagnoses, with sadness sometimes accompanying reframed expectations. Genetic diagnoses could change views of the child among extended family members, teachers, social service agencies, insurers, and broader communities and society. Genetic testing might also reduce delays in diagnoses of autism among African American, Latino and other children. These data, the first to examine several critical aspects of how parents and others view children with autism and other NDDs after receiving genetic diagnoses, highlight vital needs for education of multiple stakeholders (including geneticists, other physicians, genetic counselors, parents, individuals with autism, social service agencies, insurers, policymakers, and the broader public), research (to include perspectives of extended family members, insurers, social service agencies and teachers) and practice (to increase recognition and awareness of the potential benefits and effects of genetic testing for such children).