Background: It is well recognised that parents of children with autism spectrum disorder (ASD) often experience clinically significant levels of stress and depression. This study examined which ASD characteristic best predicted parental distress. Method: Parents of 109 children aged between 4 and 12 (M age = 7.89, SD = 2.43) completed self-report measures of anxiety, depression, stress, and parenting-specific stress. They also completed rating scales regarding their child's ASD characteristics. Results: This study found that the child's behavioural and emotional impairments predicted the parents' overall levels of distress (i.e., stress/tension, anxiety, and depression), but not the stress associated with parenting. Instead, the child's social impairment severity was found to predict parenting-specific stress. Conclusion: This study highlights the pervasive influence of ASD symptomatology on the mental wellbeing of the parents and the importance of assisting parents to cope with the behavioural and social impairments of their child.