The current study examined the effect of early emotion regulation and reactivity on later behavioral outcomes. Differential forms of reactivity were thought to interact with attentional control to predict internalizing or externalizing behavior. Additionally, social preference was examined as a moderator or mediator of these relations. Ratings of reactivity and regulation were obtained by mother report when the children were four years old. Social preference was obtained through peer report of likability. Finally, children self-reported on internalizing symptoms, and mothers and teachers reported on externalizing symptoms at age ten. Hierarchical regression analyses revealed direct effects of anger reactivity and attentional control on externalizing behavior and an interaction between sadness/ fear reactivity and attentional control predicting internalizing behavior. Social preference was found to mediate the relation between attentional control and internalizing behavior. Implications for future research examining the role of reactivity and regulation on maladaptive behavior were discussed