Background: Few currently available mental health group therapy programs have been co-designed with key stakeholders to meet the needs of autistic adult consumers. The current study formed part of a co-designed project with both autistic adults, and mental health clinicians. The goal of the study was to develop a fit-for-purpose mental health therapy program for autistic adults. This brief report outlines the major findings of the clinician portion of the project. Methods: Semi-structured interviews were conducted with mental health clinicians, asking about their experiences working with autistic adults and their thoughts and ideas for an autism specific group mental health therapy program. A constructivist grounded theory qualitative approach was used to analyse the qualitative data. Results: 18 mental health clinicians participated. Three main themes, and a further nine sub-themes, were identified. Main themes were: 1) capacity and experience of clinicians in identifying autistic clients; 2) how group sessions run: barriers and clinicians; 3) therapies that do/don’t work well and recommendations. Conclusions: Mental health clinicians reported varying confidence working effectively with autistic adult clients. Therapeutic alliance was discussed as key for stronger outcomes, along with a strengths-based approach and specific-skills based intervention.