One of every 68 children in the United States is diagnosed with Autism Spectrum Disorder (ASD). Moreover, ASD is diagnosed in 1 of every 42 boys and 1 in 189 girls. This disorder, characterized by social communication deficits and behavioral problems, is known to cause significant stress in parents that is beyond the stress experienced by parents of children with other disabilities or disorders. To date, research with parents of children with ASD has focused on the stress in raising the child with ASD, thus potentially missing an important, stressful event: receiving the diagnosis. Numerous negative reactions have been associated with a child receiving any highly impactful diagnosis, like Down Syndrome or childhood cancer. The goal of this paper was to explore how parents responded to receiving their child's ASD diagnosis, and discern which factors contribute to a greater likelihood that parents would report a traumatic stress response. Logistic regression analyses tested relationships among variables. History of traumatic experiences and emotion regulation difficulties were not significant predictors. Exploratory analyses determined that child's age at diagnosis to significantly increase the likelihood of parent-reported traumatic stress reaction. Other experiences, like hopelessness, anger/frustration, and grief, were also examined. Clinical implications and future research are discussed.