Group-based didactic training is a cornerstone implementation strategy used to support the adoption and delivery of evidence-based prevention programs (EBPP) by teachers in schools, but it is often insufficient to drive successful implementation. Beliefs and Attitudes for Successful Implementation in Schools for Teachers (BASIS-T) is a theory-based, motivational implementation strategy designed to increase the yield of EBPP training and consultation. The purpose of this study was to examine the longitudinal effects of BASIS-T on hypothesized mechanisms of behavior change (e.g., attitudes toward EBPP, self-efficacy, intentions to implement) and implementation and student outcomes associated with a well-established universal prevention program--the good behavior game (GBG). This pilot trial included 82 elementary school teachers from nine public elementary schools who were randomly assigned at the school-level to the BASIS-T (n = 43) or active comparison (n = 39) condition, with both conditions receiving training and consultation of the good behavior game by a third-party purveyor. Analyses included mixed-effects and multilevel growth modeling of adoption, mechanisms of behavior change, and student behavior outcomes. Meaningful effects were found favoring BASIS-T on immediate adoption of the GBG within the first month of school (74% vs. 40%) and self-efficacy (p < 0.05). These findings advance our understanding of the type of implementation strategies that complement pre-implementation training and post-training consultation in schools by identifying the importance of task self-efficacy as a mechanism of behavior change related to adoption for prevention programming.