We examined associations between basal respiratory sinus arrhythmia (RSA) in conjunction with RSA regulation with the hypothesis that their interaction would explain unique variability in children's prospective adjustment 2 years later. Participants were 176 children (98 girls; 78 boys) in middle childhood. RSA regulation was assessed through social and problem-solving challenges. Parents reported on children's internalizing and externalizing symptoms. Interactions between RSA baseline and regulation to the social stressor predicted children's later internalizing symptoms. Interactions between RSA baseline and responding to the problem-solving stressor predicted children's externalizing symptoms. The highest levels of internalizing symptoms were predicted for children with both lower basal RSA and higher RSA suppression. The highest levels of externalizing symptoms were predicted for children who demonstrated lower basal RSA in conjunction with RSA augmentation. Findings highlight the importance of the contemporaneous consideration of basal RSA and RSA regulation in the prediction of developmental psychopathology symptomology.