The aim of this study was to analyze the relevance of callous-unemotional (CU) traits in incarcerated juvenile delinquents. A sample of 160 incarcerated male youths was used. Results showed that youths with high CU traits had an earlier age of crime onset and of trouble with the law, and also had higher levels of conduct disorder. When controlling for age of crime onset, youths with high CU traits showed higher levels of general psychopathic traits and of psychopathy taxon membership as well as lower levels of prosocial behavior, but no differences were found for self-reported delinquency, crime seriousness, impulsivity-conduct problems, and general conduct problems. Also, no significant associations of CU traits with self-reported delinquency and crime seriousness were found when controlling for age of crime onset. Future studies of CU traits should take into account the specific importance of age of onset.