Educational researchers and school-based practitioners are increasingly infusing Motivational Interviewing (MI) into new and existing intervention protocols to provide support to students, parents, teachers, and school administrators. To date, however, the majority of the research in this area has focused on feasibility of implementation rather than fidelity of implementation. In this manuscript, we will present MI fidelity data from 245 audio-recorded conversations with 113 unique caregivers and 20 coaches, who implemented a school-based, positive parenting intervention. The aggregate fidelity scores across coaches, parents, and sessions provide evidence the training and support procedures were effective in assisting school-based personnel to implement MI with reasonable levels of fidelity in practice settings. Further, results suggest that MI fidelity varied between sessions and coaches and that within-coach variation (e.g., session-level variation in the quality of MI delivered) greatly exceeded between-coach variation. Implications for practice and future research are discussed. [This paper will be published in "Prevention Science."]