The aim of this study was to examine the role of psychopathic traits in the crime onset age of male juvenile delinquents. A group of early crime onset (n = 102), a group of late crime onset (n = 102), and a non-delinquent group (n = 102) were formed from a sample of 306 male youths from Portuguese juvenile detention centres and schools. Results showed that early crime onset participants scored higher on psychopathic measures, self-reported delinquency, crime seriousness and conduct disorder than late crime onset participants, and the non-delinquent participants. Psychopathic-traits scores showed significant associations with age of crime onset, age at first encounter with the law, age of first incarceration, self-reported delinquency, seriousness of crime and conduct disorder.