Objectives:: Much of the literature on diagnostic experiences of autism focuses on parental perspectives. Few studies have explored how health care professionals conceptualise parental experiences of the diagnostic process. The current study examines clinical perspectives of the diagnostic process with a focus on the perceived impact of assessment on families. Methods:: Qualitative interviews were conducted with 25 health care professionals from various National Health Service child and adolescent mental health services and general practices in the United Kingdom. Interviews were transcribed verbatim and data were analysed using a thematic approach. Results:: Two main themes were identified: (1) stress and the autism spectrum disorder diagnostic process and (2) expectations of the diagnostic pathway. The main sources of stress perceived by the health care professionals related to diagnostic delay and ambiguity around the diagnostic process, with parents facing significant hurdles in understanding their child’s behaviour. Many health care professionals also reported a struggle to navigate differing expectations of the diagnostic process between parents and clinicians, as well as managing objectivity in the face of significant distress. Parent internalised stigma and guilt was a key component of the health care professional’s perception of sources of stress around the diagnostic process. Conclusion:: The vast majority of clinicians recognised the diagnostic pathway as a significant source of stress for parents, with many hurdles and battles to finalise the process.