Background: Autistic people have a high likelihood of developing mental health difficulties but a low chance of receiving effective mental health care. Therefore, there is a need to identify and examine strategies to improve mental health care for autistic people. Aims: To identify strategies that have been implemented to improve access, experiences of care and mental health outcomes for autistic adults and examine evidence on their acceptability, feasibility and effectiveness. Method: A co-produced systematic review was conducted. MEDLINE, PsycINFO, CINHAL, medRxiv and PsyArXiv were searched. We included all study designs reporting acceptability or feasibility outcomes and empirical quantitative study designs reporting effectiveness outcomes. Data were synthesised using a narrative approach. Results: A total of 29 articles were identified. These included 16 studies of adapted mental health interventions, seven studies of service improvements and six studies of bespoke mental health interventions developed for autistic people. There was no conclusive evidence on effectiveness. However, most bespoke and adapted approaches appeared to be feasible and acceptable. Identified adaptations appeared to be acceptable and feasible, including increasing knowledge and detection of autism, providing environmental adjustments and communication accommodations, accommodating individual differences, and modifying the structure and content of interventions. Conclusion: Many identified strategies are feasible and acceptable and can be readily implemented in services with the potential to make mental health care more suitable for autistic people, but important research gaps remain. Future research should address these and investigate a co-produced package of service improvement measures.