Many people with Autism Spectrum Disorder (ASD) find the unpredictability of social situations emotionally distressing. It is likely that attending a diagnostic assessment is no exception. Social Stories are short stories that describe a social situation so that people know what to expect. They are written in a way that is accessible to people with ASD. This study will explore whether a Social Story written about a diagnostic assessment can reduce the associated emotional distress and increase people's satisfaction with the process. If so, they could be a simple way that services can better cater for their clients' needs.