BackgroundMost Brazilian schools do not have a continuous program for drug use prevention. To address this gap, the Ministry of Health adapted the European evidence-based program Unplugged to improve the drug use prevention efforts of Brazilian public schools. The aim of this study was to evaluate the process of program implementation in three Brazilian cities among middle school students between 6th and 9th grade (11 to 14 years old).MethodsMixed methods were used in this process evaluation study, including focus groups, fidelity forms, and satisfaction questionnaires. Study participants included 36 teachers, 11 school administrators, 6 coaches, 16 stakeholders, and 1267 students from 62 classes in 8 schools.ResultsThe 12 Unplugged lessons were all implemented in 94 % of the classes. However, only 57 % of the classes were completed as described in the program's manual. The decision to exclude activities because of time constraints was made without a common rationale. Teachers reported difficulties due to the amount of time necessary to plan the lessons and implement the activities. In addition, they mentioned that the lack of support from school administrators was an obstacle to proper program implementation. The majority of students and teachers responded positively to the program, reporting changes in the classroom environment and in personal skills or knowledge.ConclusionsThe Unplugged program can be feasibly implemented in Brazilian public schools. However, it is necessary to reduce the number of activities per class and to restructure the format of the standard teaching schedule to ensure that the normal academic content is still taught while Unplugged is being implemented.