Evidence has suggested that neurobiological deficits combine with psychosocial risk factors to impact on the development of antisocial behavior. The current study concentrated on the interplay of prenatal maternal stress and autonomic arousal in predicting antisocial behavior and psychopathic traits. Prenatal maternal stress was assessed by caregiver's retrospective report, and resting heart rate and respiratory sinus arrhythmia (RSA) were measured in 295 8- to 10-year-old children. Child and caregiver also reported on child's antisocial behavior and psychopathic traits. Higher prenatal maternal stress was associated with higher caregiver-reported antisocial and psychopathy scores, even after the concurrent measure of social adversity was controlled for. As expected, low heart rate and high RSA were associated with high antisocial and psychopathic traits. More importantly, significant interaction effects were found; prenatal stress was positively associated with multiple dimensions of psychopathic traits only on the conditions of low arousal (e.g., low heart rate or high RSA). Findings provide further support for a biosocial perspective of antisocial and psychopathic traits, and illustrate the importance of integrating biological with psychosocial measures to fully understand the etiology of behavioral problems.