Patients with antisocial personality disorder in outpatient treatment for substance use disorders are at high risk of drop-out. Using a randomized design, this study tested the impact of adding a brief psycho-educational program, the Impulsive Lifestyle Counseling program, to outpatient substance abuse treatment in order to prevent treatment dropout. Patients (N = 175) were recruited from 13 municipal treatment centers in Denmark, and assigned to treatment as usual or to the experimental condition. In all, 172 patients could be included in the analyses. In the intent-to-treat analysis, the risk of treatment dropout was reduced among patients randomized to the experimental program (hazard ratio = 0.63, p =.031), after controlling for age, gender, and substitution treatment status. The study supported the efficacy of the Impulsive Lifestyle Counseling program as a method for preventing treatment dropout for patients with comorbid antisocial personality disorder in substance abuse treatment Trial registration #ISRCTN67266318. (C) 2016 Elsevier Ltd. All rights reserved.