Most adolescent depression prevention programs have been tested in the USA and other Anglo-Saxon countries. Their effects in other contexts are less clear. We conducted a pilot trial aimed at testing the effectiveness of the Blues program, a brief indicated cognitive-behavioral (CB) group program to prevent depression originally developed in the USA, in French-Canadian secondary schools. CB group facilitators were endogenous school clinicians. A total of 74 students (mean age= 15.50; 66% female) with elevated depressive symptoms were randomized to CB group (n = 37) or educational brochure control (n = 37). Participants completed diagnostic interviews and surveys at pretest, posttest, and 6-month follow-up. Results showed that CB group had a large, statistically significant effect on MDD onset at 6-month follow-up. CB group also had a positive effect on depressive symptoms, intermediate outcomes (pleasant activities, negative thoughts), and one secondary outcome (improved interaction with parents) at posttest. These effects were not maintained at follow-up. This trial replicates results from a previous US effectiveness trial. The clinically meaningful effects of brief indicated CB group prevention, at least with regard to the prevention of MDD onset, hold in French-Canadian students when the intervention is implemented by school clinicians. Work is still needed to augment and maintain CB effects in real-world practice.