Drawing on the framework of social domain theory, this multi-method, multi-informant longitudinal study examined whether callous-unemotional (CU) tendencies moderated the association between U.S. 4 to 7 year olds' (n = 135; M[subscript age] = 5.65, 50% male; 75% White) ability to differentiate hypothetical, prototypical moral and conventional transgressions along theoretical criteria and teacher (n = 49) and parent (n = 128, 91% mothers) ratings of physical aggression. Deficits in domain distinction ability were associated with greater teacher-reported aggression both concurrently and 9 months later, but only for children high in CU traits. No main effects or interactions were found for parent reports. These findings build on a growing body of research demonstrating that children who use aggression in a deliberate and callous manner show deficits in their basic understanding of moral norms.