This study aims to assess the efficacy of the PSYCHOPATHY.COMP in promoting a compassionate motivation among male detained youth, also testing its role as a potential mechanism of change on the reduction of psychopathic traits. A treatment group (n = 58) and a control group (n = 61) answered a set of self-report measures on psychopathic traits, shame, fears of compassion, social safeness, self-compassion, and compassion for others at three timepoints: baseline, posttreatment, and 6 months' follow-up. Treatment participants attended the PSYCHOPATHY.COMP. Controls received the treatment as usual delivered at juvenile detention facilities. The treatment effects were tested with latent growth curve models. At baseline, no significant differences between groups were found. Results from latent growth curve models showed that condition was a significant predictor of change over time observed in all outcome measures, even after controlling for psychopathic traits scores. When compared with the control group, the treatment group showed a significant decrease on shame and fears of compassion and a significant increase on social safeness, self-compassion, and compassion for others over time (medium-to-large effect sizes; growth modeling analysis d ranging from .57 to .96). It was also observed that increases in selfcompassion and, in some cases, decreases in fears of receiving compassion, were crucial to the decrease of psychopathic traits. These findings suggest that the PSYCHOPATHY.COMP is a promising approach to promote a compassionate motivation in these youth, strengthening their rehabilitation odds. Increasing