Background. The Inventory of Callous-Unemotional Traits is a self- and other report questionnaire of callous-unemotional behaviors that is increasingly widely used in research and clinical settings. Nonetheless, questions about the factor structure and validity of scales remain. Method. This study provided the first large-scale (N = 1,078) investigation of the parent report version of the Inventory of Callous-Unemotional Traits in a community sample of school-age (first-grade) children. Results. Confirmatory factor analysis indicated that a two-factor model that distinguished empathic-prosocial (EP) from callous-unemotional (CU) behaviors provided the best fit to the data. EP and CU were moderately to strongly correlated with each other ( = -.67, p < .001) and with oppositional defiant disorder and conduct disorder (ODD/CD) behaviors (ODD/CD, EP = -.55; ODD/CD, CU = .71, ps < .001). Individual differences in EP and CU behaviors explained unique variation, beyond that attributable to ODD/CD behaviors, in peer-, teacher-, and parent relationship quality. Moreover, whereas EP moderated the effects of ODD/CD in the prediction of student-teacher relationship quality, CU moderated the effects of ODD/CD in the prediction of peer and parent relationship quality. Conclusions. Results are discussed with respect to the use of the ICU with school-age children.