Support for the clinical importance of callous and unemotional (CU) traits has grown considerably in recent years, yet tools for the assessment of CU traits in clinical settings have largely been limited to questionnaires. This study examined the validity of the Clinical Assessment of Prosocial Emotions (CAPE 1.1), a newly developed clinician-rating measure of CU traits in children and adolescents. Participants were children aged 3 to 15 years (N = 82; 75% male) who were referred for treatment of conduct problems. Diagnoses of conduct disorder and oppositional defiant disorder were formulated based on semistructured diagnostic interviews prior to treatment. The CAPE 1.1 was scored based on structured interviews administered jointly to mothers and fathers and was validated with questionnaire measures of CU traits and other correlates of CU traits from multiple informants. Evidence of criterion validity was found in significant associations between CAPE 1.1 scores and questionnaire measures of CU traits completed by mothers, fathers, and teachers. Evidence of construct validity was found in significant associations between CAPE 1.1 scores and established correlates of CU traits, including severity of oppositional defiant disorder/conduct disorder symptoms indexed via diagnostic interview with parents, teacher ratings of proactive aggression, and reports of affective empathy by mothers and fathers. These findings provide support for the clinical utility of the CAPE 1.1 and its inclusion as part of a comprehensive assessment of children and adolescents with conduct problems. (PsycInfo Database Record (c) 2020 APA, all rights reserved).