Objective: The main goal of this study was to evaluate the long-term effects of a brief group cognitive-behavioral (CB) adolescent depression indicated prevention program through 2-year follow-up, relative to CB bibliotherapy and brochure control, when high school personnel recruited students and delivered the program. Method: Three hundred seventy-eight adolescents (M age = 15.5, SD = 1.2; 68% female, 72% White) with elevated self-assessed depressive symptoms who were randomized to CB group, CB bibliotherapy, or educational brochure control were assessed at pretest, posttest, and 6-, 12-, 18-, and 24-month follow-up. Results: By 2 years postintervention, CB group participants showed significantly lower major depressive disorder (MDD) onset versus CB bibliotherapy (10% vs. 25%, respectively; hazard ratio = 2.48, p = .006), but the incidence difference relative to brochure controls (17%) was nonsignificant; MDD incidence for bibliotherapy and brochure controls did not differ. Although CB group participants showed lower depressive symptoms at posttest versus brochure controls, there were no effects for this outcome or for social adjustment or substance use over 2-year follow-up. Moderator analyses suggested that participants with higher baseline depressive symptoms showed greater long-term symptom reductions in the CB group intervention versus bibliotherapy. Conclusions: The evidence that a brief CB group intervention delivered by real-world providers significantly reduced MDD onset versus CB bibliotherapy is potentially encouraging. However, the lack of MDD prevention effects relative to brochure control and lack of long-term symptom effects (though consistent with results from other depression prevention trials), suggest that the delivery of the CB group should be refined to strengthen its effectiveness. What is the public health significance of this article? This study is the first to compare 2 CB adolescent depression prevention interventions with a minimal intervention control in real-world settings. The brief CB group program appeared more effective in preventing adolescent MDD than a bibliotherapy approach, but was not superior to an educational brochure, suggesting that more refinements are needed to effectively deliver evidence-based prevention outside of tightly controlled research trials.