The present study examined a newly developed intervention for conduct problem youth with callous unemotional (CU) traits. Specifically, we examined the effects of a mental models intervention designed to increase motivation, raise positive emotion, and decrease interpersonal callousness in youth. We then measured change on the treatment scale of a risk and management measure for young offenders, namely the Risk-Sophistication-Treatment Inventory – Self Report (RSTI-SR; Iselin & Salekin, 2008). The design of the study involved administering a test battery to youth in a secure residential facility pre-, mid-, and post-treatment. Findings showed increases in positive emotion and treatment amenability scores and reduced psychopathy scores across the intervention. Reductions in symptoms were evidenced across the facets of interpersonal, callous and impulsive psychopathy traits. Similarly, gains on the RSTI-SR treatment scale were multidimensional. The current study revealed three important findings. First, positive emotion was shown to increase in youth across the intervention. Second, the new intervention was effective at reducing interpersonal callous traits in youth, as well as improving their amenability to treatment. Third, the RSTI-SR appeared to be an effective measure for indexing change. Copyright © 2012 John Wiley & Sons, Ltd.