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. This study aimed to (1) explore the experiences of parents/carers seeking help from Child and Adolescent Mental Health Services for their autistic child's mental health difficulties, and (2) gain parents' perceptions of the accessibility of Child and Adolescent Mental Health Services for their child. A mixed-methods survey design was used. In total, 300 parents/carers took part from across the United Kingdom. Quantitative data were analysed using descriptive statistics, and qualitative data using qualitative content analysis. Findings demonstrated ongoing struggles that parents/carers faced when seeking help from Child and Adolescent Mental Health Services. Those who were referred reported a lack of reasonable adjustments and offers of ineffective or inappropriate therapies. Ultimately, parents felt their child's 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. There is a need for a more neuro-inclusive and personalised approach in Child and Adolescent Mental Health Services. Further research, funding and training are urgently needed to ensure support is accessible, timely and effective for autistic young people.