Underage drinking is an important public health issue for American Indian and Alaska Native (AI/AN) adolescents, as it is for U. S. teens of all ethnicities. One of the demonstrated risk factors for the development of alcohol use disorders in AI/AN is early age of initiation of drinking. To address this issue a randomized trial to assess the efficacy of Motivational Interviewing (MI) compared to Psycho-Education (PE) to reduce and prevent underage drinking in AI/AN youth was developed and implemented. Sixty-nine youth received MI or PE and 87% were assessed at follow-up. For teens who were already drinking, participating in the intervention (MI or PE) was associated, at follow-up, with lower quantity × frequency (q × f) of drinking (p = 0.011), fewer maximum drinks per drinking occasion (p = 0.004), and fewer problem behaviors (p = 0.009). The MI intervention resulted in male drinkers reporting a lower q × f of drinking (p = 0.048) and female drinkers reporting less depression (p = 0.011). In teens who had not started drinking prior to the intervention, 17% had initiated drinking at follow-up. As a group they reported increased quantity × frequency of drinking (p = 0.008) and maximum drinks (p = 0.047), but no change in problem behaviors. These results suggest that intervening against underage drinking using either MI or PE in AI/AN youth can result in reduced drinking, prevention of initiation of drinking, and other positive behavioral outcomes. Brief interventions that enhance motivation to change as well as Psycho-Education may provide a successful approach to reducing the potential morbidity of underage drinking in this high-risk group. (PsycINFO Database Record (c) 2017 APA, all rights reserved)