Background <p>Autistic people are overrepresented in eating disorders services and often require more intensive and extended treatment. Little is known about the eating disorder treatment experiences of autistic young people. The aim of this research was to understand the child and adolescent eating disorder treatment experiences of autistic people and parents of autistic young people.</p> Methods <p>Constructivist grounded theory was employed. Nine autistic people with lived experience of an eating disorder as an adolescent as well as nine parents of autistic young people engaged in paediatric eating disorders treatment were recruited through purposive sampling and then interviewed using a semi-structured design. Each interview was transcribed and analysed to identify themes and develop emergent theory directly from the data.</p> Results <p>Two major themes emerged (1) Misunderstood and (2) Safe and supportive eating disorder treatment for autistic young people and their families. Being ‘Misunderstood’ was found to occur across eight different domains including problems related to diagnosis, misattribution, neuro-normative definitions of eating and recovery, a one size fits all approach, siloed expertise, limited expertise and treatment options for eating disorders outside of anorexia nervosa, family neurodivergence and autism not being accommodated. The effects of being misunderstood included an increased burden of case management and advocacy, distress and trauma, mistrust of health professionals, identity disruption, and setbacks in recovery. ‘Safe and supportive eating disorders treatment for autistic young people and their families’ is informed by lived experience and built on a foundation of general care principles and autism-specific elements.</p> Conclusions <p>Being misunderstood is a recursive process that occurs across multiple aspects of eating disorder care. Autistic young people and their families desire and need safety and understanding. This is achieved through care characteristics that promote connection and nuance, and autism specific adaptations and accommodations that provide optimal support conditions and strengthen therapeutic alliance.</p> Trial registration <p>This research was approved for prospective registration on Open Science Framework (OSF) on the 8th December 2023.</p>