A number of studies have identified discrepancies in informant ratings of externalizing behaviors in youth, but it is unclear whether similar discrepancies exist between informants when rating psychopathic traits. In this study, we examined parent–child agreement on ratings of both psychopathic traits and externalizing behaviors, and examined the factors that influence agreement in both of these domains. A total of 282 children between 7 and 16 years (M = 10.60 years, SD = 1.91) from an outpatient child psychiatric clinic participated in this study. Our findings revealed low levels of parent–child agreement on these measures (ICC values ranging from .02 to .30 for psychopathic traits; ICC values ranging from .09 to .30 for externalizing behaviors). In addition, our findings did not support the moderating effects of child’s age, gender, clinical diagnosis, informant, and parental conflict on the relationship between parent- and child-ratings of psychopathic traits and externalizing behaviors. Further research is needed to better understand how parents and child reports of child’s externalizing behaviors and psychopathic traits are similar and/or different from one another and factors that influence these agreements.