This study evaluated the effectiveness of acceptance and commitment training (ACT) for increasing drug and alcohol counselors' willingness to use evidence-based agonist and antagonist pharmacotherapy. Fifty-nine drug and alcohol counselors were randomly assigned to either a 1-day ACT workshop or a 1-day educational control workshop. Both groups then attended a 2-day workshop on empirically supported treatments for substance abuse. Measures were taken at pre- and posttraining and 3-month follow-up on reported use of pharmacotherapy, willingness to use pharmacotherapy, perceived barriers to implementing new treatments, and general acceptance. As compared with those in the education alone condition, participants in the ACT condition showed significantly higher rates of referrals to pharmacotherapy at follow-up, rated barriers to learning new treatments as less believable at posttraining and follow-up, and showed greater psychological flexibility at posttraining and follow-up. Mediational analyses indicated that reduced believability of barriers and greater psychological flexibility mediated the impact of the intervention. Results support the idea that acceptance-based interventions may be helpful in addressing the psychological factors related to poor adoption of evidence-based treatments.