The present study examined the contribution of early reactivity and regulation on externalizing behavior in preadolescence. Moreover, subcomponents of attentional control (i.e., attention shifting and attention focusing) and negative reactivity (i.e., sadness and anger) were examined individually to test whether a specific combination of factors uniquely contributed to the outcome. A subset of data were utilized from the ongoing, longitudinal RIGHT Track project (N = 404), in which parents reported on individual factors at age 4 and teachers reported on externalizing behavior at age 10. A hierarchical linear regression analysis revealed a significant interaction between anger reactivity and attention shifting when controlling for early externalizing behavior, where children with high levels of anger and low levels of attention shifting experienced the greatest increase in externalizing behavior over time. An increased focus on specificity is needed in research on the interplay between reactivity and regulation in the prediction of externalizing behavior.