OBJECTIVE: The study aimed to assess the effectiveness of an 18-hr cognitive behavioral group intervention in reducing depressive symptoms (and associated outcomes) in a universal sample of students in mainstream schools in England. The intervention, the UK Resilience Programme (UKRP), was based on the Penn Resiliency Program for Children and Adolescents. METHOD: Students (N = 2,844; 49% female; 67% White) were ages 11-12 at 16 schools. Classes of students were assigned arbitrarily into intervention (UKRP) or control (usual school provision) conditions based on class timetables. Outcome measures were the Children’s Depression Inventory (Kovacs, 1992) (depressive symptoms, primary outcome); Revised Children’s Manifest Anxiety Scale (C. R. Reynolds & Richmond, 1985) (anxiety); and child-reported Goodman (1997) Strengths and Difficulties Questionnaire (behavior). Students were surveyed at baseline, postintervention, 1-year follow-up, and 2-year follow-up. RESULTS: At postintervention, UKRP students reported lower levels of depressive symptoms than control group students, but the effect was small (d = 0.093, 95% CI [-0.178, -0.007], p = .034) and did not persist to 1-year or 2-year follow-ups. There was no significant impact on symptoms of anxiety or behavior at any point. CONCLUSIONS: UKRP produced small, short-term impacts on depression symptoms and did not reduce anxiety or behavioral problems. These findings suggest that interventions may produce reduced impacts when rolled out and taught by regular school staff. We discuss the implications of these findings for policy and for future dissemination efforts.