The link between autism spectrum disorder symptoms and maternal stress has been well established, yet many mothers remain resilient to more severe psychopathology. For the current online study, 111 mothers of a child with autism spectrum disorder completed questionnaires about their child's symptoms, their own stress related to parenting, and any psychopathology symptoms they were experiencing. Autism spectrum disorder symptom severity was positively related to both parenting stress and maternal psychopathology symptoms. Furthermore, parenting stress mediated the relation between autism spectrum disorder symptom severity and maternal psychopathology symptoms. These results provide evidence for a pathway through which psychopathology may develop among mothers of children with autism spectrum disorder and a potential point of intervention for clinicians serving this population.