The etiology of oppositional defiant disorder (ODD) is not well understood but appears to have both biologically-based roots and can develop following adverse experiences. The current study is the first to examine the interaction between biologically-based factors and type of trauma experience (i.e., interpersonal and non-interpersonal) and associations with ODD. The psychophysiological factors included baseline resting heart rate, respiratory sinus arrhythmia (RSA), and cortisol. ODD was measured as two dimensions of irritable and defiant/vindictive. The sample included 330 children, 3-7 years-old, oversampled for a history of trauma. Results showed the interactions between baseline physiological arousal variables and trauma type in predicting ODD dimensions were not supported. However, the baseline RSA by trauma interaction was a significant predictor of defiance/vindictiveness among boys, but not girls, when interpersonal trauma was compared to controls. Several other gender differences emerged. Among boys, both interpersonal and non-interpersonal trauma were predictive of ODD dimensions; however, among girls, non-interpersonal trauma was not. Among girls, there was a significant negative bivariate relationship between baseline cortisol and irritability. Also, when the sample was restricted to those with interpersonal trauma only and controls, baseline RSA was negatively associated with irritability in girls only (controlling for trauma). Finally, retrospective reports revealed that children who met criteria for ODD diagnosis and experienced interpersonal trauma were more likely to exhibit ODD symptoms prior to their trauma compared to those who experienced non-interpersonal trauma. Results are discussed in the context of previous mixed findings, and avenues for future research are highlighted.