The American College of Surgeons has mandated that level I and level II trauma centers implement universal alcohol screening and brief intervention (SBI) for injured patients. This study was a secondary analysis of a national, 20-hospital, cluster-randomized implementation trial focusing on practical issues of training and supervising alcohol SBI providers in motivational interviewing (MI). The purpose of this study was to examine whether real-world trauma center providers can be trained to provide higher quality counseling using MI as part of brief interventions for alcohol and whether MI skills can be maintained over time. Sites were randomly assigned to receive a 1day workshop training in MI for alcohol SBI or not, and all providers regardless of training completed up to seven standardized patient assessments of MI fidelity over 27months. Six domains on the Motivational Interviewing Treatment Integrity (MITI) coding system were assessed and compared to proficiency criteria. Providers in the intervention training group showed substantially improved MITI scores over the course of the 27-month time period. Domains that had particularly strong improvement were MI spirit and empathy; however, despite the overall improvement in the intervention group scores, expert-derived proficiency criteria were attained only for the global scores. Routine trauma center providers who receive MI training can deliver higher quality counseling in alcohol brief interventions, but may not, however, attain previously derived proficiency standards. Future implementation efforts in real-world acute care medical settings could further elucidate provider characteristics that predict training response and also strive to demonstrate that higher quality alcohol SBI implementation is associated with improved patient-level outcomes.