We report an evaluation of a combined individual- and community-level treatment and prevention effort to reduce underage drinking by American Indian (AI) youths on rural California Indian reservations. The interventions included: brief motivational interviewing and psychoeducation for Tribal youths, restricting alcohol sales to minors in alcohol sales outlets, and community mobilization and awareness activities. Surveys were collected from 120 adults and 74 teens to evaluate the awareness and effectiveness of the interventions. A high proportion of adult (93%) and youth (96%) respondents endorsed being aware of one or more of the intervention activities, and 88% of adults and 71% of youth felt the program impacted the community in a positive way. Eighty-four percent of adults and 63% of youth agreed that as a result of the activities that they decided to take action to reduce teen drinking in their community. Being aware of more of the intervention activities significantly increased the odds of taking action to change drinking behaviors. This study documents that a significant proportion of the community was aware of the intervention efforts and that awareness caused them to take action to reduce underage drinking. Such efforts may benefit other AI/AN communities seeking to reduce underage drinking.