Parental problem drinking (PPD) is associated with various forms of child psychopathology, including hyperactivity, conduct disorder, delinquency, depression and anxiety. However, not all children share the same risk for developing adjustment problems in the context of PPD. In this study, we examined patterns of sympathetic and parasympathetic nervous system activity account for differential susceptibility to the adverse effects of PPD in middle childhood. We found that reciprocal SNS activation protects against child internalizing symptoms in the context of mother problem drinking. We also found consistent interactions between PNS and SNS in predicting child internalizing problems. Coinhibition is linked to more internalizing symptoms including anxiety and depression. This study provides further support for Autonomic Space Theory and demonstrates the importance of taking both PNS and SNS into account when studying physiological response to stress.