Oppositional Defiant Disorder (ODD) is commonly conceptualized as a disorder of negative affect and low effortful control. Currently, it is unclear whether temperament and personality traits associated with negative affect and effortful control can be useful assessment tools for identifying ODD early during development. This study examined the relationship between temperament and personality traits and ODD in a clinical sample of preschoolers. Results suggest that, at this age, temperament and personality traits of negative affect and neuroticism and effortful control and conscientiousness/agreeableness are not associated with one another. High negative affect, low conscientiousness, and low agreeableness were all specifically associated with the angry/irritable (vs. argumentative/defiant, vindictive) ODD symptom domain; however, the traits did not predict change in symptoms over time. Lastly, low conscientiousness predicted ODD-related impairment, while negative affect and agreeableness interacted to predict impairment such low agreeableness appears to be a primary pathway to impairment, and high negative affect appears to be a secondary pathway. Overall, this study suggests high negative affect, low conscientiousness, and low agreeableness are associated with ODD. Early assessment of these traits may be clinically useful in identifying children at risk for ODD, given that they may be early markers for ODD symptoms and impairment.