Autistic people experience more health conditions and earlier mortality. This study investigated views about a primary care health check for autistic adults to inform its design. Fifty-one people participated in consultation groups and interviews, comprising autistic adults (some with co-occurring intellectual disabilities), adults with intellectual disabilities, supporters and health professionals. Participants wanted the health check to cover physical and mental health and social functioning. They emphasised the importance of sharing information about individual needs and associated adjustments before the health check. They highlighted the need to change the way healthcare services communicate with autistic people, such as reducing phone contact and booking appointments online. They wanted individual choice in how the health check was completed, with video call or email offered alongside face-to-face. Participants raised the need for further training of primary care staff on autism, to highlight the diversity of experiences of autistic people and ways in which difficulties, such as pain, may present differently. Clinicians raised questions about the capacity of mental health and social care services to meet the additional needs potentially identified through the health check. This study represents a key step in the development and co-design of a UK primary care health check for autistic people.