In this study, we examined the role of negative emotionality as a moderator of the relations of effortful control and overcontrol (versus undercontrol) with children's externalizing problem behaviors; we also examined the longitudinal relations among these variables. Teachers' and parents' reports of children's negative emotionality, effortful control, overcontrol and externalizing problem behaviors were obtained at T1 (N=199; M age=89.51 months) and again 2 (T2) and 4 years (T3) later. In addition, children's effortful control was assessed with an observed measure of persistence. In a T3 concurrent structural equation model, effortful control, but not overcontrol, was negatively related to children's T3 externalizing problem behaviors. In regression analyses, the negative relation between T3 effortful control and externalizing problem behaviors was strongest at high levels of T3 negative emotionality. In the best-fitting longitudinal structural equation model, both T1 effortful control and T1 overcontrol negatively predicted externalizing problems at T1, whereas T3 effortful control (but not T3 overcontrol) was significantly negatively related to T3 externalizing problem behaviors when controlling for T1 externalizing problem behaviors.