Previous research has shown the relevance of psychopathic traits as predictors of severe and persistent antisocial behavior. Given that personality traits refer to developmental constructs, the main purposes of this study were to analyze the stability of psychopathic traits from childhood to adolescence, and to examine differential outcomes derived from distinctive pathways of stability and change. Data was collected in a Spanish sample of 138 children aged 6–11 at the onset of the study (T1), and 12–17 in the subsequent follow-up conducted 6 years later (T2). The stability of psychopathic traits was assessed in terms of differential continuity (rank-order), absolute stability (mean-level) and individual-level change (Reliable Change Index). Results confirmed that psychopathic traits remained moderately to highly stable from childhood to adolescence (p < .001). There were, however, some differences depending on the informant (parents vs. teachers) and the particular assessment method used (rank order vs. mean-level and RCI). A stable high and an increasing developmental pattern of psychopathic traits were related with severe adolescent behavioral and psychosocial problems (ŋ² = .10–.36). These results support the usefulness of youth psychopathic personality as a developmental construct, and highlight its relevance as a predictor of long-lasting maladjustment, with relevant implications in terms of prevention and treatment.