ABSTRACT Aims The effectiveness of expert-led (EX) and train-the-trainer (TT) strategies was compared to a self-study approach (SS) for teaching clinicians motivational interviewing (MI). Design Twelve community treatment programs were assigned randomly to the three conditions. EX and TT conditions used skill-building workshops and three monthly supervision sessions guided by treatment integrity ratings, performance feedback and coaching techniques. Trainers in TT were first trained and certified in MI and then prepared carefully to deliver the workshops and supervise MI at their programs. Clinicians in SS only received the training materials. Setting Licensed out-patient and residential addiction and mental health treatment programs in the US state of Connecticut were involved in the study. Participants Ninety-two clinicians who provided addiction treatment within these programs and had limited experience with MI participated in the study. Measurements Primary outcomes were the clinicians' MI adherence and competence and the percentage of clinicians meeting clinical trial standards of MI performance. Assessments occurred at baseline, post-workshop, post-supervision and at 12-week follow-up. Findings The study found EX and TT, in comparison to SS, improved clinicians' adherence and competence significantly, with higher percentages of clinicians reaching clinical trial standards of MI performance and few differences between EX and TT. Conclusions This study supports the combined use of workshops and supervision to teach community program clinicians MI and suggests the train-the-trainer approach may be a feasible and effective strategy for disseminating empirically supported treatments.