Motivational interviewing (MI) is an evidence-based intervention with considerable support for promoting behavior change across a broad range of health and mental health issues. Despite its effectiveness, challenges associated with learning the approach may limit its full implementation in many clinical settings. The aim of the present study was to evaluate a supervised MI training practicum implemented within a doctoral internship/postdoctoral fellowship training program. The goal of the practicum was to enable each trainee to achieve expert competence in MI. Participants were 29 psychology doctoral interns and 1 postdoctoral fellow who participated in the training as part of their internship or fellowship program. Training included an initial workshop followed by a supervised practicum during which progress toward an a priori established expert competence benchmark was tracked through the use of an established coding system. Results indicated that trainees were satisfied with the supervision received. Three trainees did not achieve the a priori benchmark due to schedule conflicts. The 27 trainees who achieved the benchmark required between 4 and 20 supervision sessions to do so (M = 9.22, SD = 3.77). With the exception of reflective listening skill, prior training, baseline skill, and self-reported motivation were not associated with number of supervision sessions required to achieve the benchmark. Implications for training and dissemination of MI in clinical settings are discussed.