Background Autistic children and young people are at increased risk of mental health difficulties, but often face barriers when seeking help from Child and Adolescent Mental Health Services (CAMHS). There is limited literature exploring the accessibility of CAMHS for autistic young people, particularly from parents perspectives. The present study aimed to 1) explore the experiences of parents/carers seeking help from CAMHS for their autistic childs mental health difficulties, and 2) gain parents perceptions of the accessibility of CAMHS support for their child and understand what could be improved. Methods A mixed-methods survey design was used to learn from parents/carers. 300 parents/carers took part from across the UK between June and October 2023. Quantitative data were analysed using descriptive statistics, and qualitative data using qualitative content analysis. Results Findings demonstrated the ongoing struggles that parents/carers faced when seeking professional help from CAMHS for their child. Many were not referred to CAMHS or were rejected without an assessment, often due to issues relating to diagnostic overshadowing, a high threshold for assessment, or a lack of professional knowledge about autism and care pathways. Those who were referred reported a lack of reasonable adjustments and offers of ineffective or inappropriate therapies, leaving young people unable to engage, and thus not benefiting. Ultimately, parents felt their childs mental health difficulties either did not improve or declined to the point of crisis. However, there was a recognition that some professionals were kind and compassionate, and provided the validation that parents needed. Conclusions There is a need for a more neuro-inclusive and personalised approach in CAMHS, from the professionals themselves, in the adjustments that are offered, and in the therapies that are provided. Further research, funding, and training are urgently needed to ensure mental health support is accessible, timely, and effective for autistic CYP.