Purpose: Both the resting heart rate (RHR) and the callous-unemotional (CU) traits have been associated with juvenile delinquency, however the effect of their interaction is not yet clear. Methods: Four hundred and twenty-three institutionalized adolescents divided into early adolescents (10–14 years, n = 133), late adolescents (15–17 years, n = 286), and young adults (18–22 years, n = 136) participated in the study. RHR was measured using a wristband, and CU traits and delinquency history were assessed using self-reported questionnaires. Moderation analysis was performed to understand how the combination between RHR and CU is associated to offending. Results: CU traits were associated with offending at all ages. The interactions between RHR and CU traits were significantly related to the likelihood of offending in the early and the late adolescent. The highest likelihood of offending is related to high CU traits combined with low RHR in early adolescents and with high RHR in late adolescents. Conclusions: These findings provide further insight in the relationship between psychopathic traits and biophysiological maturation in explaining juvenile delinquency.