The current study assessed whether reactions to diagnosis are associated with health status for mothers of children with autism spectrum disorder at the time of diagnosis, and whether such diagnostic-reaction resolution status is associated with changes in health status over time. A total of 84 mothers of children newly diagnosed with autism spectrum disorder, with stable reactions to diagnosis over a year, participated. Their perceptions of their physical and psychological functioning, and quality of life, were taken at the time of diagnosis and 1 year later. The mothers were also given the Reaction to Diagnosis Interview. Mothers who had an unresolved reaction to diagnosis had a worse health status in terms of their perception of the physical symptoms at the time of the diagnosis, and showed worsening levels of health over the period of a year, relative to mothers who had a resolved diagnostic status. These relationships were independent of other potential predictors of ill health in this sample. The findings point to the potential of the diagnostic process to negatively impact parental health. Given that this can have negative consequences for child prognosis, as well as parental health, there is a need to develop better understanding of the impacts of diagnostic practices.