This study examines to what extent baseline school climate moderates the effects of a randomized controlled trial of a universal violence prevention intervention. School climate was assessed by teacher ratings of the quality of relationships among school members and the seriousness of school problems. Cluster analysis revealed three climate types: distressed, average, and conducive. Mixed‐effects regression models of data from 5,256 students suggested limited overall positive program outcomes for students in schools assigned to the universal intervention versus students in schools assigned to control conditions. There was, however, evidence of differential effects of the universal intervention by climate type. These findings have important implications for identifying school characteristics that researchers and practitioners should consider in planning universal school‐based interventions.