Parents of autistic children experience significant parenting stress, which is prospectively associated with increases in child externalizing behaviors. However, family factors that place specific families at risk for experiencing the negative impacts of parenting stress on child externalizing behaviors have not been identified. The present study examined whether parental mental health moderates the association between parenting stress and child externalizing behaviors. Parents of 501 autistic children (Mage=5.16yrs) completed the Parenting Stress Index and Eyberg Child Behavior Inventory. Parents reported whether they had ever been diagnosed with a mental health disorder. Parenting stress, parental internalizing diagnosis, and parental externalizing diagnosis all independently predicted child externalizing behavior. However, parenting stress did not interact with any category of parental mental health diagnoses to predict child externalizing. Results implicate high levels of parenting stress as a risk factor for increased child behavior problems among autistic children across parental mental health statuses. Interventions aimed at reducing parenting stress may improve parent outcomes and prevent the development of child externalizing behaviors among families of autistic children.